Totallymeh

First off, I'm quite sorry if I put this in the wrong section but I'm getting desperate... I've been googling all afternoon and I'm not sure what to do. I have a minecraft account and it's installed with version 1.6.2. I however would like to try the Ars Magica mod which requires 1.5.2 so I downloaded the forge 1.5.2 universal file. Every website and youtube video tells me to copy ALL the files in this rar file into a copy of my minecrafts jar, located in Appdata/roaming/.minecraft/versions and then put that jar and the other file in a folder sharing a name with these 2 files. After that I put the rar file of Ars Magica in my mods folder but my game continues to crash on every start up. I must be missing some key element to this! Any and all help is appreciated, but please do not direct me to the search button.. I've been using it all day and I'm sure I'm entering the wrong things. Thank you!