First, Open RM (obviously)
Depending on whether or not it's been used before, you may have to select the option at the top "Flash ClockworkMod Recovery". If that's the case it's pretty cut and dry, just let it do it's thing.
After that the most
important step is:
SELECT BACKUP CURRENT ROM!!!! Name it what ever you like and hit OK. Let it do it's thing. DO NOT SKIP THIS STEP!! If something happens when flashing this ROM this backup is you fail-safe!!!!
Then:
1) Select Download ROM
2) From there you'll see a list of developers. Select which one you want, Ill use Sapphire 1.0 as an example because, well, I am bias :biggrin:
SO, the dev of Sapphire is cvpcs.
3) After selecting the dev, you'll see a list of their current ROMS (most recent at the top). So, in this case select Sapphire 1.0.0
4) It'll run through a list of extras. As my personal rule of thumb I try not to do to much at once when flashing a ROM for the first time. In other words, no theme, stock kernel, etc. So, at the kernel choice just hit OK. Theme, select stock. Now, ROM addons - you need Google Apps (market, gmail, etc). The "enable stagefright" has to do with streaming audio quality and Froyo (2.2). If you stream music a lot select it, if not you may not need it.
5) Let it all download.
6) After it's done a box will pop up - you'll have to select wipe data/cache (you may want to backup all you're apps prior to any of this, sorry I forgot to mention that at the top. Appbrain is good for that or Astro file manager has a backup apps feature too). You won't need to backup cuz you did that already. Hit OK and away you go!!
7) After it's done you'll have to activate the phone again and your apps should reinstall from the market. If not, that's where the backups come in play.
I recommend after you get everything back and running (apps installed, home screens setup, wall paper applied, etc.) you make another backup with RM! Remember, these backups may say your a$$ one day
Typically I'll run a ROM for a couple of days before trying to install a theme or a kernel. This way you have a feel for the ROM, then if you intstall a kernel and things act weird, it's a safe bet it's the kernel and not the ROM.
I know it seems overwhelming, but you'll get the hang of it. The hardest part is jumping into it the first time. But, if you do get stuck there is always a way around it and theses forums are GREAT!