A paper wallet is a temporary convenience that allows you to buy bitcoin if you don't have an online wallet. It is highly recommended that you transfer all of your bitcoin from the paper wallet to an online wallet as soon as possible.
Although each online wallet will have a slightly different way of doing it, the process for transferring bitcoin from a paper wallet is straightforward and simple. You will use your online wallet to import the bitcoin from the paper wallet by scanning the private key's QR code on the paper wallet with your online wallet app on your phone. Select the amount of bitcoin to import to your online wallet (remember that you should import all of the coin on the paper wallet) and approve the transfer. Your online wallet's balance will increase and the balance on the paper wallet will now be zero.
Once this has been completed, destroy the paper wallet. Do not use it again!
Since each online wallet has a slightly different way of doing this, more detailed instructions can be found for each of these popular wallets:
There are other wallets that can be used; however, not all wallets allow paper wallets to be imported