Well, first, Download the file
from the official website.
when you extract the file it will probably be a folder. In that folder should be the BIOS file for flashing, and instructions on how to do it. In your case, scroll through the instructions until you find the AMI section. Every BIOS and board has some different steps, so it's important you follow the instructions closely.
As for OC switches? Not sure, though generally it's preferred that you go look up some guides on BIOS OCing with the board and CPU instead of relying on preset switches.