Installing garage door springs is NOT recommended unless done by a trained professional. This article will attempt to describe the process but does not in any way suggest it should be done on ones own. Please call a professional for this job!! You can be severely injured if done improperly.
It is extremely important if you attempt to install your springs that you are a DIY veteran and that you are not in over your head. The incorrect installation of springs has been known to injure people who simply did the wrong thing. If you are at all unsure about how to install your springs, call a professional. If you think you can do it on your own, make sure you follow the manufacturers instructions to the letter.
First, if you are in the process of replacing an old door, and removing old springs, especially torsion springs, you want to be extremely careful. These old springs are very powerful used to lifting a 400 lb. door and if they are rusted or difficult to remove, they could cause injury. Once you have the old springs out of the way and are ready to install the new door, you want to completely unpack everything that came with your new door. There will be lots of individual parts and usually a list of everything that is supposed to be in the box. Make sure that you have all of your pieces present before you start otherwise, you could find yourself in a sticky situation later.
You spring will sit on your torsion bar, so make sure that you have your door set up and your upper brackets in place before you even consider installing your springs. Every manufacturers instructions are a little bit different than the next, so be sure that you follow their instructions to the letter. Installing a new garage door can be done by one person to a point, but you will need at least one extra set of hands eventually. This is the part where you might want to call over a friend or two.
You may need to install extra support brackets for your torsion bar depending on the weight. Again, every door is different and if the walls of your garage are not as sturdy as they should be, you may want to go with the extra brackets just in case. Some kits come with extra brackets, but some do not. Next, you want to run the lift cable up to the drums that you have installed near the spring, and then cover each end of the bar with a tube retainer. Carefully install the winding unit that puts the torque on the spring you need for it to function correctly. It is the release of this torque that often makes replacing these springs so dangerous. If you make a mistake here, you may want to call in a professional to fix it. Once you have enough winds on your spring, you want to test it by lifting the door just a few inches and screw in the set screws that were blocked when the door was closed. Test the door by lifting it all the way up and adjust your springs as needed.
Again, this article is simply a simulated guide to explain how the job is done. You should never attempt to replace a garage door spring without the help of a qualified professional.