Close the operating panel -- the part of the door that slides -- and lock it.
Unscrew and remove the head stop. This is the piece along the top of the doorframe that keeps the door in place.
Unlock the door and open it partway.
Lean the top part of the door towards you and lift it out of the sill track along the bottom of the doorway.
Remove the screws from the stationary sill filler. This is located on the bottom track along the wall frame to which the stationary panel is adjacent.
Unscrew the head bracket and remove it. This is located in the top corner of the stationary panel.
Move the stationary panel past the center of the doorframe and lift it out of the frame by the bottom.