Ken, If you got the commercial version, I found the instructions very detailed and useful. That said here is a quick rundown of it's use.
There are basically two settings to use, one for each different "exercise.
1. Set the length of the string/rope on the FM to be about 3" shorter than than the distance from your string arm elbow to the string. With this shorter setting, hook the rope on your bow string, put the straps on your arm so one strap is above your elbow and one below. The straps should "cradle" your elbow. Now with your fingers OFF the string and your string forearm RELAXED, draw the bow using ONLY your elbow. This will teach you a rotational draw and force you to draw with your upper back shoulder area and back and when you get it back you will find the weight of the bow being supported on your bones. Do this frequently and learn a really good draw technique. You will find this very difficult to do with a "hunting "weight bow so start with a light bow if you can.
Second, reset the length of the string/rope to be about 2 or 3" LONGER than the distance from your elbow to the string. Now you can use an arrow or not, your choice. Come to full draw using the feel you learned from the short string set up but with your fingers on the bow string as normal. The FM will have a small loop of the rope hanging below your forearm from elbow to bow string. Come to full draw and release. DON'T WORRY, THIS IS NOT A DRY FIRE!!! The strap on the FM WILL try to pull your string arm elbow forward -- DON'T LET IT. If you do this part correctly, you will learn what you must do to absolutely NOT let the strap pull your arm forward. Try to "resist the strap" as you release. After this exercise, take the FM off and shoot a few arrow really duplicating the feelings you got with the FM on. You will find a more efficient draw, better alignment, and better follow through.
Like any tool, you will get out of it what you put into it. And, probably some sore muscles in the next day or two. Good luck.