Be patient it takes a lot of pushing and pulling even with a helper.
How to install bottom garage door seal on metal door.
If you have a wooden garage door rip off the nailed rubber seal.
Install the new seal with the larger sloped edge to the outside of the garage door and the flat part against the bottom of the door.
Thread the t shaped edges into the weather seal track then slide the seal across the door.
Clean the door bottom photo 2 then cut the new rubber seal to length with a razor knife.
Tips on replacing your garage door bottom seal.
He also gives a brief description.
Make sure you have the right weather seal for the retainer the retainer is the metal strip on the bottom of the garage door that has a track for the weather seal.