Eagle is 'orrible isn't it. Nothing works like a standard windows program. I'm changing to Design Spark when I can figure out how to import my eagle projects and libraries – get rid of that 100mm square limit!.
As for your problem, the answer is totally anti-intuitive!
Place your gates, and then right click one of them and choose 'invoke', now select PWRN and it will let you place power connections.
Don't ask me how I remembered how to do that, I suspect its because it took me four days to figure out how to do it…
Yep, Eagle is the most user-unfriendly Windows program EVER!
Neil