The new spring s diameter length and wire size or gauge must be the same as your old spring.
How to fix a garage door extension spring.
How to repair garage door springs and cables lock down the door.
Loosen the unbroken spring.
Wipe off any excess then repeat the process on the other side.
Spray each spring with garage door lubricant.
A garage door weighs tans and it would be close to impossible to move it shut and open without the help of the door springs.
Clamp a locking pliers or a c clamp to the track just above one of the rollers.
Purchase new garage door extension springs.
The easiest way to do this is to take the broken spring to a local garage door dealer or home improvement center so they can help you find an exact match.