Many seals interlock with a groove in the door and simply pull away. If yours is glued down, slide a putty knife under the seal to break the adhesive bond. (You don’t need to reglue the new one.) ...

Exterior-facing doors are especially prone to drafts. The Suptikes Door Draft Stopper Under Door Seal uses flexible silicone ...

To remove the old seal, start at the top. Grab the edge that's on the inner side of the door and pull it upwards. You should see a retaining plate that is attached with hex screws under the gasket.