If you are logged in to the AW website (you have registered with the AW site to have a username and password), you can make the add yourself by going here:
Just (repeatedly) reposition the map, and zoom in until you can locate the put-in (when zoomed in far enough it will let you click on the river), then move the map until you can locate the take-out (click on that spot), and the software should 'map' the run. Then fill in the rivername, a section name (usually street names or access area names), pulldown to pick what class/rating it is (at normal, usual, boatable flows), and provide a description (basic overview of the run). If there are named rapids/features, generally don't list them in the 'description', but add them later. (It's really a two-step process ... (1) create the listing (using the 'river creator'), then (2) 'flesh out' the listing, by pulling it up from the regular AW page, clicking the "Edit" (pencil icon at left under title banner and river map), to then edit the description, or click "Add Feature" (to add detail about put-in, take-out, rapids, and other 'points of interest' along the run).
Otherwise (if you don't have a userid or if you have trouble doing the above), if you can post some basics here (or reply directly to me, or any other prominent poster on the forum here) with latitude/longitude coordinates or other description of of put-in and take-out locations and other 'basics', one of us can do the 'add', and get it listed.
Also ... if you've got some photos of some of the run, they can be added (once the description is created) by doing a "Trip Report".