There are two covers on the carb one is pressed steel and one is cast:
Connect the nipple on the cast cover to the engine back plate.
The nipple on the pressed steel cover is too atmosphere.
The nipple on the side of the carb is connected too the tank, no other connection too the tank from the engine.
The tank is vented to atmosphere, take the vent line up over the top of the tank so that it will not allow petrol to siphon out when you get fuel in it during aerobatics.
I use a three pipe system in my tanks with the third pipe to the bottom of the tank for filling and emtying this is Plugged after filling.

Mike