It's not really recommended unless you can find the same ROM that your phone has now on the Herald Wiki (so you can restore your ROM in case you brick your phone).
But if you still want to proceed, there's tons of info already in the forums.
I've read the instructions on bottom of the post: Extract file, copy ASerg Policies.CAB to PPC and Run it,then reboot driver.
Sync PPC to PC and run 1__UPGRADE_ROM.bat,Wait it 10-15 minutes.
Cheers..!