Bob, if you open the link you just provided and look on pages 6 and 7, the answer to your question is contained in those installation instructions. Note Detail D where the spring tension is held with cotter pins until mounted and ready to deploy. Apparently, your awning had the pin removed prematurely during installation, or the spring is broken.
What isn't apparent is whether the awning has a separate spring for each end, or if there's one central spring that should operate both arms evenly. If separate, you should be able to take the end cap loose and wind it up to tighten. See page 6, "Attach The Arms", Steps 1 and 2. If that doesn't work, you probably need to replace the spring.
Ken & Jeannie - 96 Vectra Grand Tour 35' DP Freightliner 6 spd Allison Jack (silky terrier), Hannah (poodle), Casey (Cairn Terrier)