One the Billet model, connect the rad to the hole that will fill the bottom of the can. As it fills, if the level gets too high, the internal tube that extends to the top will be the overflow drain tube. It should be exposed to air or you can attach a drain hose to deposit the overflow on the road rather than your foot.
I have the Weapon-R tank. The hose connected to the rad runs down to a nipple on the bottom of the tank. The upper nipple comes with an overflow hose attached.
Weapon-R
btw, do you have a link to the Billet Specialties model that you posted a picture of?