You said you tried it but you don't say what is the problem you get...
did you install retroarch addon?
can you launch it?
These steps has no difficulty more than install a repo and selecting an addon from it to install, there is nothing to configure and nothing to try.
If you have retroarch installed (it takes about 3 minutes to install it) you should just launch it from addon section in kodi, thats all.
If you get some kind of error or problem, you must tell us in gamestarter´s thread what your problem is and we will try to help you.
Once you control retroarch then you can install AEL or Emulationstation as a frontend for your game collections and scrape them, but first I recommend you to get familiar with retroarch, you can find a lot of tutorials in the internet.