Using a paper clip or tweezers, pop out the screen by pressing the plastic tab in the top-left corner of the phone's bottom casing as indicated in the photo.
Be careful not to lose the tab that pops out. It is a small and clear piece of plastic.
As shown in the photos, pull the orange strip through a thin opening at the top of the phone. Once this is done, the top and bottom halves can be separated.
Carefully open the casing using the iFixit plastic tool by prying each side a little bit at a time. Rotate and open until all the inside clips pop open and the casing opens up.