Specifically, you should use the Rags 2.4.16 download. That's been more stable than any of the version 3 Rags engines IMO. You will probably unzip the setup folder and run a setup.exe or something like to install Rags game player on your machine. Once finished, in the folder where it installed should be a ragsplayer.exe or similar. Launch it, then open the game file from inside the Rags Player. Depending on your operating system, you may need to check the help thread here or at Hypnopics Game Zone to get Rags to run.
Cheating under the Rags engine required using Cheat Engine (I think) or having the Rags developer suite installed (which includes the Game Player), and launching the game within the developer console to open the debugging window(s). There should still be a thread at Hypnopics which has some more in depth instructions.