The new lenses should have come in a kit. The kit would include 2 rolls of black butyl sealer and a handful of metal clips. When you peel off the old lenses, note where the original metal clips are. Pry off the old metal clips, then with a flat head screw driver start peeling/prying off the old butyl sealer as best as you can (take your time). get it all off!
Unroll one of the rolls of the new butyl sealer and work-it/stick-it around the outside of the slotted grove where the original sealer was and where the new lense will meet with the box housing.
***I went out to a autoparts store and bought some clear sylicon sealer in a tube. Before I put my new lenses in, I but a nice bead of the sylicon sealer around the edges of the lense on the part that will fit into the slot where you just added the fresh butyl sealer. This extra sylicon will help improve/tighten the fit and will add as extra protection for where there may be some tiny spaces between the plastic and the butyl sealer where water or moisture could get in behind the lenses.
Lastly, and this is crucial, buy a roll of duct tape! Once you install your new lenses in (sealer and all), use strips of duct tape to help keep your lenses in place and to stop them from possibly popping out or not staying seated properly while the new butyl sealer and sylicon "cure/dry". While adding firm pressure to keep the lenses in place, take strips of the duct tape and tape them across the lense and stick the other end to the housing on top. Nice and snug.
Leave the tape on the lenses and try not to drive the car for at least 24hours as this is generally how long it takes for the sylicon to cure properly. When the 24 hours are up, gently peel the tape off and your new lenses are good to go!!!!
I spent a whole evening doing this job on my car and didn't drive it for 2 days. On the 3rd morning I took the tape off. They hold great
Good luck.