Authorize.net How do I use this?

Ok so I have experience in html and css and a little php. I have been busting my ass figuring out everything with opencart and authorize.net.

My main problem is telling opencart that I want it to use authorize.net SIM. I see in my opencart 1.4.7 that authorize.net AIM is installable under the payment modules extensions menu. But what about SIM? I have been digging through all the different files trying to just figure something out. I cant even find a simple step by step set up. I totally understand a lot of how this works I just cant figure out step one really. I can get all the php file sin the right place but how do I tell opencart to use them in the first place? I find it shocking that this info is so hard to find, I have been digging around and reading all day.

Please help me. Just a simple step one step two and so on. I got my authorize.net account and my keys and all that jazz and I have already modified my php files to more or less how they should be. But I cant even tell cause I cant figure out how to tell opencart to use it.

The only working sim module is available here

Ok I just bought and installed it. I am going to spend some time figuring out all my steps and any bugs I may need to fix and then I will post what I had to do to get this thing up and running so other people who are in my position can benefit.

Ok getting stuck with an error 13 like I see a lot of people have. I figured it out though, I got my test account API login and pass mixed up with my real one. I wasnt aware but apparently when the SIM admin interface is set to test you still want to use your real trans. key and login.

Im sure this is not the end but Im glad I figured that out on my own.