Start with the lock-side to establish the proper compression, and, as you install the hinge side of the seal, use a little less compression of the foam seal. If you compress the hinge side too much, it will get caught and pinched the first time you open and reclose the door. As you install the top seal, the compression will match that of the lock-side as well as the hinge side, which means it will have a slight taper to it.
The door itself can be removed and placed on saw horses so that you can remove the bottom seal. On newer doors, it is common to have a vinyl seal along the bottom of the door that is held in by two grooves in the door along with a staple at each end. Remove this seal and replace with the same style, available at home centers and building supply stores.
If you have a problem with weather-stripping on an older style door, email me and let me know, and I will address it in another column. With the new weather-stripping in place, it will last longer if we could somehow train our dogs to ring the doorbell.