Welcome to NuFi wallet's knowledge base. Learn more about NuFi (and access the wallet) on our homepage here or ask a question in our Discord server here.

Your ADA is never locked. You are free to move your ADA at any time. Therefore, to increase or reduce your staked amount, simply transfer funds in or out of the staked account. Any ADA that is added is automatically staked and requires no further action. 

For more information about Cardano staking, please see here.