Ok, so what exactly is your problem? chandujram linked the beginners guide, where you may find that you need RSDLite (the flashing tool) and a SBF file to flash matching your phone and region
(and provider if you want) - both are linked in the thread. Follow the instructions to flash the SBF to your phone and you have Froyo/Gingerbread. This thread
should give you a clue, what SBF is Froyo or Gingerbread - and what bootloader they bring. you have read and understood, that certain bootloader versions come with some restrictions
, haven't you? Good. Then follow the instructions in the thread for the rom you posted.