Lay out a string line to help you get the first row of paint circles straight. Just remember to line it up in the direction you want the Twister field to be. Also make it at a minimum the length of the Twister field. You really only need this for the first row of paint circle.
Just pound in two stakes and run a string between them. That's all you need. If you don't have stakes you can always use two trees to run the string between.