It takes a couple hours for the name to be registered. Blockstack will issue two Bitcoin transactions in the background, and it will wait for the first one to be confirmed before sending the second one. You need to leave your computer online during this time for it to go through. You can check its progress using any Bitcoin block explorer by inputting your wallet address, and you can confirm whether or not it is registered by searching for it at explorer.blockstack.org. Hope this helps!