Sideskirts install with 5 screws in the bottom of each, plus a bead of adhesive along the top edge. Holes for the screws are pre-drilled and it is advised to pre-install the skirts with only the screws the first time around as they are self-tapping but can be difficult to start.
The spoiler used a few screws along the lower portion (again, holes are pre-drilled) and then adhesive to glue the upper to the lower portion, leave some small weights (I used 5lb dumb bells) on the spoiler overnight to prevent lifting. Be careful of the forward most outside edge and the very center, they are the most likely places to warp.
PM me your email and I'll send you some pictures of the process, and next time buy from someone who provides support and install instructions ;)
-Dan