Once you get the side done, start on the bottom of the phone (around the charging port)

There are 2 clips on either side of the charging port - you may have to pull away a little more than comfortable, but the plastic is quite malleable and as long as you do it with consistent pressure there should be no problem

When the top is all that's left, wiggle the back cover towards the top of the phone and it should release all clips that are still intact

Make sure you don't lose the volume rocker or power button as they are likely to fall out