To remove a handle from a storm door, unscrew the latch-mounting screws, and then pull the handles apart. It is also necessary to remove the center spindle before discarding the handle.
If installing a new handle into the storm door, it is important to ensure the measurements of the mounting holes are correct. There are three mounting holes in the door that align vertically, so measure the distance from the door's edge to the center of one of the holes. This is the backset measurement, and the new handle should have the same backset. Put the outside lever components of the handle together, following the directions that accompanied the handle, and then insert the spindle into the center, before pushing and fully installing the new handle.
It should only take about 10 minutes to install a new door handle, and it requires a cordless drill, a drill bit set and a screwdriver. A replacement door handle is also important to have, but if wood is the main material of the door, it may be necessary to purchase a handle with special hardware. It is also possible that the old strike plate is not compatible with the new handle. In this case, purchase a new strike plate that fits with the new handle before completing the installation.