After you take the drum off you lay it down (a concrete floor is good) with the cup side down. Then with an authoritative hammer (single hand sledge is good) you pound on the bad stud. A few good whacks and it should come out. Then with the new one you kinda do the reverse. The studs are designed to hold themselves when inserted into the drum. You'll want to pay attention to that lug after you've been driving though. Just tighten it once and a while to insure that the new stud seats firmly.