Typically you can unlock your wallet under Help > Debug window > Console > then type command " walletpassphrase *yourwalletpassword* 99999999 true "


- walletpassphrase = the command
- *yourwalletpassword* = your wallet password without the *'s
-  99999999 = time in seconds to keep the wallet unlocked
- true - this is to unlock for staking only or not, true enables unlock for staking

Keep in mind the coins need to be 30days+ old to stake