Don't try to fully remove the rear cover yet, as a ribbon cable on the right edge connects it to the phone.

Use the suction handle to lift the left edge of the rear cover and swing it over the right edge, like opening the cover of a book.

If you're having trouble, check the perimeter for any remaining adhesive and use your opening pick to separate it.

Prop up the rear cover with the suction handle so you can access the ribbon cable near the top right corner.