Can anyone explain to me how to add bitcoins to a cold wallet?

Have a PC that is always offline. Use Electrum to create a wallet on that offline computer. Record and save your seed. Take your public key from that wallet. Install Electrum on your online PC and restore a wallet with that public key. The one on the online PC is a 'watch only' version of your offline wallet, meaning you can use it to monitor and receive funds. You can only spend by creating the transaction on the online machine, saving it, moving and signing it on the offline machine, saving it again and moving/broadcasting that transaction from the online machine (which with your cold storage should not happen much at all). It's mostly for receiving and periodically sending small amounts of funds to your separate mobile wallet for sending day to day.

/r/Bitcoin Thread