Hi, Donna :) You don't need a pattery to do a towel :) Just decide the materials (cotton, linen, cottolin most likely) and the finished size you want (I measured my own towels), and plan accordingly. For *cotton* I allow 15% shrinkage from size on the loom to wet-finished and dried size. Linen and cottolin shrink less, but I haven't enough experience to say just how much.
Then decide a weave structure--twills can be done on 4 shafts and provide a cushier feel and better drape for wrapping around the body. Then plan your project, weave it, and tell us how it went! Holly
