This video will help you weigh a garage door with extension springs.
How to chage springs on garage door.
Once in place disconnect the garage door opener.
Do not use a digital scale as they often will not respond to the door weight changing as rollers no longer stick to the track.
Doors with extension springs have two sets of pulleys which are sometimes called sheaves.
Place the new garage door springs against the garage door position the springs so that the ends are facing you and coming from opposite directions.
The left spring should have the wire coiling from the left the right spring should have the wire coiling from the right.
Take up the left garage door spring and put it by the left side of the door.
Open the garage door to remove all spring tension and clamp it in place.
One cable attaches to the bottom of the door runs up and over the pulley above the door and around the spring pulley and then attaches to the door track bracket.