Its quite simple to do. Just remove the single Philips screw within the hatch handle. Then remove the hatch plastics, by carefully pulling them away from the hatch. Next use a 10MM deep-socket to CAREFULLY remove the nuts holding stock spoiler in place. Use the help of a friend. And take extra care not to drop the nuts in to the frame of your trunk as you remove them.
You can follow the first part of this guide and photos to assist you in removing the stock spoiler:
https://celicahobby.com/forums/ubbthreads.php/topics/18536/spoiler-apr-how-to-install.htmlIf you dont plan on replacing the spoiler with another, you'll need to plug up the screw holes and look for solutions to deal with the "spoiler dimples."
Good luck on your projects