Which year is your Escape?
The number one tip when working with plastic parts, especially those that snap together/apart: don't do anything unless the parts are warmed to at least 65˚F.
On my 2005 Escape, the quarter panel trim was secured with metal snap fittings, so it's easy to remove and install. Pull back the liftgate weatherstrip and load floor carpet, remove the rear seatback bracket bezel (the round panel covering the bracket), grasp the upper part of the quarter panel trim, and pull it away from the body. Be sure to locate any snap fittings that may fall off.
When you reinstall the quarter panel trim, there are several interlocking tabs on the panel and on the C-pillar trim, directly above it. Be sure that those tabs are lined up before pushing the quarter trim panel back into place.