Get a good bike repair manual at the book store. It'll cost you about $25.00. When you want to do a repair, tune up, or install an upgrade on your ride, read all about it first. Keep the book handy while you are doing the work, and take your time. In no time, you will be a fair hand with the wrenches.
When I was learning, it really helped to do just one job at a time. Stick with it until it's done and everything works properly. You may have to make further adjustments after your next ride. It's just part of the process. Go forward, without fear, and now that the end of season is near, watch for a sale on a set of tools. bk