Don't open the phone all the way yet. The display cable is still threaded through the mid frame and you might rip the cables of the home and menu buttons.

Start to carefully lift the upper edge of the display assembly and thread the display flex cable through the mid frame.

Check if the home button or soft key button cables sticks to the display assembly before your remove the display all the way.

In case one of the cables sticks to the display, carefully peel them of with a pair of tweezers or an opening pick.