Private keys are secret codes. Plug it into a USB port on your device. If you plan to store large amounts of currency on a desktop wallet, you should certainly place it in cold storage. Is Bitcoin a safe way to store value digitally? Whereas an OpenDime unit can be used extremely securely as an address to store Bitcoins until the owner needs to cash out, but only once. Cryptocurrencies tend to be riskier than most in a variety of ways.