If you go to the last tab ("Wallet Details"), you can insert any private key
If you go to "Wallet Details", you can't obtain the nice Paper Wallets that you can obtain in "Paper Wallet"...
Your best option is either to do as the last poster said, or manually create the nice paper wallet. Just make sure you're using a 100% javascript QR code generator, or you might end up giving your private key away. So only do this is you really know what you're doing.