you can attatch them like a normal bottom bait if you wish, on a knotless knot rig, but they may lose bouyancy as to being punctured.
another way of attatching them is by using a d-rig.you tie a knotless knot rig, and make a hair abou 2-inches long without a loop. you then thread on a rig ring, pas the hair back through the eye of a hook and blob it down with a lighter. you then tie on the bait to the rig, using dental floss or weak line, ie 4lbs.
maybe someone with more knowledge of d rigs can explain them better, as i rarely use them.
i am more confident in just using a standard hair rig for mounting them, as i don't leave baits on for more than 2 hours, and nash say their pop ups don't loose bouyancy due to puncturing.
tight lines
courtz