Be careful! The spring holds a lot of tension. You will need to unwind it to release the tension using the arm before you take it off. Zipdee can give you instructions if you email them.
When the awning is installed, the slats are installed on the trailer first, then the awning and last slat are slid in. It took us 3 people to install ours start to finish. (21 ft awning) The arm is wound at the end. We didn't get enough tension on ours the first time around and that's why the wind almost claimed her on I70 last spring. You need enough tension to wind the awning up with a finger push but not so much you have to hold it down when you open it.