Treat a paper wallet like a piggy bank: Add funds as often as you like, but only import (or "sweep") your funds once.
How to transfer bitcoins to a paper wallet
Open your live wallet software (e.g. Mycelium, Bread, Trezor) or web-based wallet (e.g. blockchain.info, coinbase.com) and send funds from your live wallet to the public address shown on your paper wallet. After transferring the funds, search for your public key on blockchain.info to see the progress of your transaction.
How to withdraw/spend bitcoins using a paper wallet
The way you will access your funds will be to "import" or "sweep" your paper wallet. This effectively transfers the coins from your paper wallet to a live wallet (e.g. Mycelium or Trezor) or to an exchange service (e.g. Coinbase.com). You should always sweep the complete balance, as it's generally not safe to try to spend just a portion of the funds on your paper wallet.
Virtually any wallet software or Bitcoin service that includes a "import private key" or "spend from cold storage" feature will accept the private key hidden beneath the folds of your paper wallet. However, not 100% of wallets have this feature. For example, Coinbase.com cannot directly sweep your paper wallet. In this case, it is recommended that you use software such as Mycelium (Android) or Bread (IOS) to sweep your paper wallet and send the funds to your Coinbase
Important note for BIP38-encrypted paper wallets
Not many bitcoin wallet applications or web services are able to directly import BIP38 password-protected private keys. In this case, you will have to use the "Validate" feature on the generator to extract the unencrypted Wallet Import Format (WIF) key as an intermediate step before sweeping the balance.
Example of spending from a paper wallet
Let's say you have some Bitcoin on paper wallet and you want to sell it on Coinbase. Here's how you might accomplish that:
- Install and set up a trustworthy Bitcoin wallet on your phone, for example using Mycelium (for Android) or Bread Wallet (for IOS)
- Now, using a different device (e.g. your laptop) find your Coinbase receiving address. Login to Coinbase, go to 'Accounts' and then click on the 'Receive' button for your Bitcoin account. This will display a QR code on your screen.
- Now open up your paper wallet to reveal the private key and QR code. Now, scan your private QR code using your phone's wallet software. (In Mycelium select the menu option "Cold Storage". In Bread, go to Menu : Settings : Import Wallet)
- In the case of Mycelium, you will be able to send your funds directly to your Coinbase receiving address with a single transaction. In the case of Bread wallet, you will first import the funds into Bread, and then you will be able to send your funds to Coinbase (costing you two transactions.)
Your paper wallet may contain additional "free" cryptocurrency!
Depending on when your paper wallet was funded, it may hold cryptocurrency balances besides your Bitcoin. This may result in significant added value to your paper wallet. At the time of this writing (January 2018) any paper wallet funded before October 2017 will have been gifted up to three valuable cryptocurrencies other than Bitcoin, amounting to an additional $2,500 USD of value per Bitcoin.
