Fuel goes in between 1-2 on the DOHC CV carbs.
The "T" between 2-3 just needs to vent to air unless you're using the auto-petcock. You can stick a hose on it and run it out of the way (you could just leave it without a hose on it, but I'd be worried about stuff dropping into my carbs).
There is also a nipple close to the engine around carb 1 (location is from memory) that needs to be capped unless you're using the auto-petcock.
Many people took the auto-petcock off their bikes, so you might not have it (I've taken mine off and it runs much better, but I suspect mine was in poor shape and failing).
1981 CB750K with 900 cams
90K KM's, rebuilt head, rebuilt carbs, upgraded valve stem seals
My wife's recipe website that I'm trying to help promote:
Strawberries for supper. Yes, I am a lucky man.