In short you install Clockwork Recovery, Download a ROM and move it to your phones internal memory, and flash the ROM in Clockwork.
Head over to XDA-Developers forum, go to the Software Development section of the Vibrant forum. There you will find a hand full of custom 2.2 ROMs from different developers. Which one you choose is totally your preference, read through the descriptions of each ROM and choose. Feel free to try as many ROMs as youd like. More detailed instructions on flashing ROMs can be found in that forum also.
Even though the post get long over there keep reading. Many roms look nice and have cool added features but have little issues that can be deal breakers or things stripped you may like and use. MMS issues are common. Wifi seems to be a issue on some as well as visual voicemail not working and GPS seems to works different on them all.
Hello!! I have a Samsung Vibrant Galaxy S through Tmobile. I have been reading about the Froyo 2.2, and I want to update my phone with the operating system. I am really new at this and I was wondering if anyone could show me how to install it on my phone?