All testers have ratings, so you can make sure you are getting top-notch results. To get meaningful feedback, beta testers are promted to rate you in all areas of your project (graphics, ease of use, etc.).
Convert your scratch project into a flash file. (Projects converted using Junebeetle's converter.)
Upload your project. Now you can give it a name and a description. You are even able to choose whether testers can download the original project!
Select beta testers or have testers find your project. Soon, you will have lots of great feedback to work with!