There are dozens of previous threads and posts about winterizing RV's already here on the forum. If you do a forum search and type in "winterizing", I'm sure that you will come up with enough reading material to keep you busy for quite some time. Some of the threads and posts outline step-by-step instructions that members have submitted for their Keystone model.
Overall, the steps are very similar from model to model.
Also, Keystone has a video on winterizing and this can be seen by going to their website (
www.keystonerv.com) and finding the links to their various videos.