That part is slightly more complicated. But I'll try to clear it up for you:
1) XP = Download ActiveSync if you don't already have it. Vista = Download Windows Mobile Device Center if you don't already have it
2) Be sure to flash to CF03 FIRST!
3) Download 'Samsung Omnia UDML' from
this site (it's linked over on the right side of the page, bout halfway down)
4) Download the custom 6.5 ROM you want from your favorite chef's thread (like the one you linked to earlier). Usually when you download the file it will be in either .rar or .7z format. You'll need to unzip it first, after which it will be in .bin fomat.
5) If using XP, open Active Sync and go into settings and disable the 'Allow USB Connections' setting. If using Vista, do the same but do it in Windows Mobile Device Center Settings
6) Open UDML (the one you downloaded from idoctor)
7) Click the 'PDA' button on the left and search for the .bin file you just downloaded from the chef. Click 'Open'
8 )Turn off your phone (completely off!!! not just asleep)
9) Click the 'Detect' button toward the bottom left of UDML
10) While still off, plug your phone into your computer via USB
11) Turn the phone on
12) Let the utility run for about 5-10 minutes to complete the flash
Congrats! You are now on a custom 6.5 ROM