I have no idea how to use the steam anything o_O

What version are you running? I ask this because the steam system is brand new and has been changed frequently since its first implementation barely a month ago.

First, you'll need a source of heat. If you are using the steam system to cool down a reactor (to get an extra 50% EU output... eventually), you'll first need to upgrade your reactor to the new 5x5 size with Pressure Vessel blocks. You'll need to fill your new reactor by putting IC2 Coolant into the reactor liquid port. IC2 Coolant is made from Water (or Distilled Water) and Lapis Dust, enriched in a Canning Machine. Now when you run your reactor, the internal heat vents will be converting IC2 Coolant into IC2 Hot Coolant rather than simply producing EU.

Then you'll need to pump IC2 Hot Coolant into Liquid Heat Exchangers (LHE). You'll need to put those copper Heat Exchanger items into the LHE GUI, up to a maximum of 100 Heat Units per tick (HU/t). The LHE won't start working immediately. There is a face of the LHE with a orange square, which is the heat Output side. The side needs to be connected to another machine that will accept heat, such as a Steam Generator. Once there's a place for heat to go , the LHE will start converting IC2 Hot Coolant back into IC2 Coolant, which you can send back to the reactor.

The Steam Generator (aka steam boiler, because it's generating steam from water) can be filled with Water or Distilled Water (more later). It accepts heat from any side, which can be provided by a Liquid Heat Exchanger or any of the other Heat Generators. Inside the boiler GUI, there are two controls: a pressure valve, and a water feed valve. The water feed should be kept very low, either 1 or 2 millibuckets per tick (mB/t).

Based on the water feed rate and the input heat rate, you'll need to adjust the pressure valve to ensure a constant steady flow of steam. If the steam comes out in spurts, you'll need to adjust the pressure valve. Remember your basic fluid physics - the higher the pressure of the system, the hotter the water will need to be before it turns to steam. If the boiler gets hot enough (over 374°C) you'll start getting Superheated Steam instead of regular steam, which contains more energy and thus produces more power.

Here's a cheat-sheet for the two "best" settings for the boiler:
Heat input: 100HU/t, Water Feed: 1mB/t, Pressure: 0 bar => cheapest setup for 100mB/t of steam
Heat input: 200HU/t, Water Feed: 1mB/t, Pressure: 220 bar => the cheapest setup for 100mB/t of Superheated Steam possible. Note that you will need two LHE's pointed at the boiler.
note: these numbers will possibly change in the near future as the system undergoes balance passes

Note that when using regular Water, the steam boiler will slowly become calcified. Speaking realistically, this is because when water is boiled it will leave any dissolved solids behind. Those deposits can build up and ruin your boiler. Currently there is no simple fix for a Calcified boiler, but I assume in the future you'll be able to replace its tubing or wrench it, or something.

The steam boiler will try to output its steam automatically, so there's no need for a Fluid Ejector. You'll probably want to put the steam straight into a Steam Kinetic Generator (aka steam turbine). I suppose you could use the steam in another mod, assuming IC2 steam is Ore Dictionary compatible, but I'll stick to turbines.

You can place the turbine block adjacent to your boiler and the steam will be transferred automatically. The turbine block will need a turbine rotor in it's GUI before it will function, and it will need somewhere to eject its "exhaust" steam.
- if the steam is "regular" steam, the exhaust should go to a Steam Condenser (more later).
- if the steam is Superheated, the exhaust should go to another turbine, where it will be treated as regular steam. Thus, this is a "two stage" turbine setup.

If there is nowhere for the steam to exhaust to, the turbine will cause "heat explosions" which do not destroy blocks but will hurt nearby players. Once the steam turbine receives steam it will start producing Kinetic Units of power, again at the orange square on its side. As the turbine operates, some of the steam will condense to Distilled Water on the blades of the turbine, slowing it down. You'll want to use fluid ejectors or pipes to remove the water and keep the turbine running at full speed. To convert the turbine's KU output to EU you'll need a Kinetic Generator. These are pretty self explanatory.
- 100mB/t of steam will normally produce 50EU/t.
- 100mB/t of superheated steam will produce 100EU/t in the first stage and 50EU/t in the second stage (150 total).
note: these numbers will possibly change in the near future as the system undergoes balance passes

The condenser has a "passive" ability, but it probably won't be able to keep up. You'll need to add Heat Vents to its GUI and supply the condenser with EU for it to speed up. The Condenser converts steam to Distilled Water. Distilled Water has two uses:
a) It takes less Lapis Dust to make IC2 Coolant
b) It can be boiled in a steam boiler without causing calcification.
The condenser can also accept steam directly from a boiler, if you want to produce distilled water with minimum hassle.

I hope this answers your questions.

Yep, sorry about that. I was in a hurry when I wrote that. The kinetic output side has a white circle. I think the exhaust will go in any direction so long as there's a turbine or a condenser there, but I honestly don't understand that part of the code very well.