First get a length of sealing strip for your door, at least 1 foot longer than the width of the door. Now remove the door as follows. The screen is held to the wall where it slots into a vertical holder that is screwed into the wall. Look along the vertical holder and you will find some screws on the inside or outside of the holder (may have caps on them that need removal to expose the screw heads). Remove these screws while someone supports the screen, the screen can now be removed. There is a groove along the lower end of the screen which holds the round part (not the blade) of the seal. You probably will need to cut the holding knot at the wall end, note how it is done before doing so. Now remove the old seal. Prepare the new seal by cutting away a 4" section of seal, leaving the round rubber part, thread the new seal in with the round rubber part leading, it comes through a hold in the end of the groove so you can knot it or otherwise fix it. Cut the seal to length. Now slot the door with the new seal back into the vertical holder and redo the holding screws, you are done!