Do you have a custom recovery installed? If not, that would be the first thing you should look into doing.
Next step would be to make backup(s).
- Optionally you could make a backup with titanium backup or something similar (my backup for example).
- The other backup being one in recovery, I personally don't consider this one optional this is a must.
The next step will be to follow the instructions for installing whatever ROM you have chosen. Usually this requires wiping data/cache (done through recovery) but sometimes there are other steps prior to flashing the ROM. Sometimes there are steps after flashing the ROM (like GApps for example). Most, if not all ROMs will have a general installation instruction guide.
That is the general idea at least.
Do you have a custom recovery installed? If not, that would be the first thing you should look into doing.
Next step would be to make backup(s).
- Optionally you could make a backup with titanium backup or something similar (my backup for example).
- The other backup being one in recovery, I personally don't consider this one optional this is a must.
The next step will be to follow the instructions for installing whatever ROM you have chosen. Usually this requires wiping data/cache (done through recovery) but sometimes there are other steps prior to flashing the ROM. Sometimes there are steps after flashing the ROM (like GApps for example). Most, if not all ROMs will have a general installation instruction guide.
That is the general idea at least.
If you use ROM manager you probably have a custom recovery, as you can't really use it without clockworkmod recovery installed.
If you have a custom recovery, all you need to do is find a ROM you want to install, download it to your sdcard and then follow my steps. Backups, then whatever directions the ROMs say. Usually it is something like, reboot into recovery, wipe data and cache, install *insert name of ROM*.zip from sdcard, reboot into Android.
[video=youtube;s3HCzX9YBz0]http://www.youtube.com/watch?v=s3HCzX9YBz0[/video] <-- that video is for a different phone but it shows the general idea.