LOL... you can't you need to be on fw 3.55 or less... so put it back to shop get your money back... and ebay and buy slim 3.55... then come back to ps3 news... 4.31 will never get hacked for multiple reasons... hope this helps
Sadly, Superslim and even newer slim models (CECH 3xxx and one of the more recent 2xxx I think) comes with a new set of keys and security issues fixed, you can't hack them even with flasher as It won't downgrade back to 3.55. If you're serious about CFW and homebrew, your best bet is what credentialz said, get a used one on ebay already at 3.55.
credentialz: Tell me one reason. It could get hacked, It's just that nobody ever done It yet... After people finding the Lv0 I started getting quite optimistic.
not sure i'd ever say never with hacking the ps3, always someone coming up with something new, im not sure the new process that hasn't come out yet, where you play backup games on ofw from a ext hd is limited to 355, wasn't clear last time i read, you'd have to check, but yea, i'd trade it in for something on 355
as said you can't do it. the lv0 key stuff only applies to older models. new ones have a new key, and even if the public key is found it won't help because the cryptographic mistake sony made has been fixed, so you cant find the private key from the public key with the math that fail0verflow used the first time.
the private key needs to be taken from sony to sign cfw the so console will boot it. its very unlikely that this will ever happen. older console FTW.