There are two-way to do this. The first way is to simply go Settings>Unlock Wallet and that’s it

However, we would advise that you do it another way so that you have your wallet unlocked, but still have it encrypted. This way, you will still need to input your paraphrase in order to send any coins out of your wallet. Much safer. To start Staking whilst retaining the security of your wallet, go Help>Debug Window. Now select the Console tab. Type the following at the bottom:

"walletpassphrase YourPassphrase 9999999 true"

Replace the YourPassphrase that I have added in red with your own passphrase. (the encryption password you added earlier on) The 9999999 relates to the amount of seconds that you wish to leave the wallet open for staking. Once you have added this hit Enter.

You will see that the information was added correctly.

[Important] Now hit the Red bar next to where you entered your text, to clear the information from your console. CTRL + L will do the same thing. Don’t worry this won’t affect Staking, but it will prevent people who may have access to your machine or wallet looking at your wallets console window to see if there are any traces of your passphrase. Always clear any text that you add to the console for security purposes.

The text will have been removed now so close the console area by hitting the red X.

You will now see on your Wallet Overview that your wallet is unlocked but still encrypted and Staking away. Once you start to receive any coins you earn via Staking, they will require 510 confirmations from the network.

Please note that the more coins you have in your wallet, the more likely you are going to be able to start Staking. If you only have a small amount of coins in total (eg. 0.1 BC to 100 BC) then your weight on the network will also be small and you will find that Staking may take considerably longer. The more coins you have in your wallet, the greater the weight of those coins will be. This is also why some people may see that their coins maybe showing as immature, even though they have been trying to Stake for 24hrs+.