First of all make sure you have an after market cooler on the Fx 8320.
If you are using the stock cooler that came with your Amd Fx cpu it may limit how much you can overclock.
Heat is the enemy, once you start to overclock a cpu, so the name of the game is cooling for starters.
FX chips are Multiplier unlocked.
So it`s a case for a simple overclock of the cpu to just change the multiplier of the cpu.
You should be able to manually set the multiplier value if at 3.5Ghz it should be 200 x 17.5= 3.500 or 3.5Ghz
If you up the multiplier to the value of 18 then you simply x the 200 by 18 to get the core speed of your cpu.
Make half multiplier changes, save the settings in the bios and test to see if windows loads without any errors...