In order to regsiter an ENS username ( <yourname>.stateofus.eth ) you need to have both 10 SNT and a little bit of ETH (for gas) in your Status wallet to make the required Ethereum transaction.
The name will be unique and yours until you decide to let it go, upon which you will receive your original 10 SNT back into your wallet.
@Tidus who is also a Status Ambassador created a guide for buying SNT.
Check it here: https://buyingstatus.com/