Inspect door frames for gaps and holes that may need sealing. If there are any holes or cracks on the exterior side of the door around the frame, seal them with caulk rated for outdoor use. Insert the caulk tube into a caulking gun, cut off the end with a utility knife at an angle and push the gun’s plunger against the bottom of the tube. Pull the trigger to release the caulk and pull the gun across the area you want sealed.
Clean the entire area inside where the weather stripping will be added. Use mild detergent, water and a sponge, making sure no dirt or grease remains. Remove old weather stripping and any old adhesive. The old weather stripping should just pull off. For stubborn adhesive, apply a glue and adhesive remover with a rag and scrub it away. Be sure to read all manufacturer instructions to be sure the product is appropriate and won’t damage wood or other areas. Dry the area with a clean cloth.