4 Door

WARNING: This page is about a different car, the 2004 Mazda 3. However, it is still accessible from the selected car via links, so may be relevant.

Remove the nuts.
While cutting the double-sided adhesive tape using a flathead screwdriver or a razor, separate the rear spoiler from the trunk lid.
WARNING:
- Using a razor with bare hands can cause injury. Always wear gloves when using a razor.
Pull the rear spoiler upward, then disengage clips A and tabs B from the trunk lid.
Remove the rear spoiler.
Install in the reverse order of removal.

Fig 1: Rear Spoiler - 4 Door With Torque Specifications
Courtesy of MAZDA MOTORS CORP.
1. Attach double-sided adhesive tape to the rear spoiler as shown in the figure.
  
  Fig 2: Attaching Double-Sided Adhesive Tape To Rear Spoiler
  Courtesy of MAZDA MOTORS CORP.