Start by adjusting the track to move the door closer to the wall. If you look at the bracket holding the track near the top, there's a horizontal slot at the bottom with two screwheads in it. Loosen those (and any other screws in horizontal slots), push the track so the door-to-wall clearance is a little less than the thickness of whatever weather strip you use, and tighten everything. The track is supposed to be at a slight angle that, as the door descends, pushes the door evenly against the weatherstripping.