we are on the same network. im at my friends house.
You both need to be playing the same mod pack, and on the same network (wireless connection) or if you are trying to play with network cables, I find it easier just to plug the 2 computers into each other.
Then one of you needs to load a game, go into the pause menu and press "Open to LAN", then when the other person opens the multiplayer screen, wait a few seconds (up to a minute), the other player's "server" should automagically appear *if you are using the latter method.
Read lenscas' suggestion for the wireless/non-connected suggestion