Right, as Sinnaj said, you can look at the API for how the energynet works -- specifically, in ic2/api/energy/usage.txt, which is a very detailed explanation of how it's intended to work.
If you want some code to look at, I'll point at my Interdictor tile entity from BeamMeUp. It does a few things more than just connecting to the ENet, but it should otherwise be a reasonable reference implementation.
I'm not sure how I feel about the use of this forum vs. the Support forum for API questions; they really do both work, though I suspect the Support forum gets more eyes.