The rear badges come with 3M tape. You just peel the cover off and stick.
When you pull the old label off the body, use nylon string or dental floss. Next, I use a pre-paint VOC cleaner available from Eastwood. It works faster than any other solvent (goo off, etc) at removing all traces of old adhesive, but not cured paint. I lightly press on the badge on one corner and step back to verify straightness. If you only press one corner, you can slightly rotate the badge. The front badge needs to removed with tools. Easist way is to remove the front bumper. I'm waiting for my Levels intercooler before I replace my front badge. Hopefully this weekend.