1. Lock your wallet if it's already unlocked for staking.
2. Unlock your wallet using your passphrase and uncheck the For Staking Only box.
3. Click Help, then click Debug Window
4. In the bottom of the window type dumpprivkey your wallet address (ex. dumpprivkey PSj5h4tTTgmz9LHcuD5689ABJS7T3HFF7f). Make sure there's a space between dumpprivkey and your wallet address. Hit ENTER.
5. You will see your PRiVCY wallet private key in the window.
Paste that into a new document and save it with a file name such as privcyprivatekey. Then I'd store it on a USB flash drive or hard drive that's encrypted using Veracrypt or something similar.
After doing this, you might want to also back up your wallet, which is very easy.
1. Click File, click Backup Wallet.
2. Save the .dat file with a filename such as privcybackup7.18.18.
I'd also store this on your encrypted USB or hard drive. You really should backup on a regular basis.