Well your probably running installs through SPRecovery and ROM Manager runs them through Clockwork Recovery. If you dload ROM Manager open the application and the first thing you will have to do is install CLockwork Recovery by hitting the clockwork recovery button. It will show a progress bar and let you know what version you are running when installed. Since you only have the free version the only rom you will beable to download I believe is the CYANOGEN rom. The paid version of ROM manager will open up a list of many other roms for you to try and is well worth the money. Anyway if you want to install Cyanogen install the latest 5.0.6.2. First create a backup by selecting backup my rom then you just need to touch the download rom button then touch the cyanogen button next select the cyanogen rom version you wish to download. MOST IMPORTANTLY when prompted select install google apps if you do not you will not have any google apps installed on our phone including the market place. Once you do all this it will dload the rom and reboot your phone into Clockwork where the rom will be installed. Once finished Clockwork reboots your phone and viola your done! Its that easy with rom manager. Again the paid version rocks it has overclocking kernels, the baseband radio update, many many roms, and lots of themes to lay over cyanogens rom all installable with the press of a button!