If you are already delegated to a validator, but for some reason you want to change the validator you are staking to (also: see this how to choose a validator to stake to article). You can follow these steps to redelegate to another validator.
Side note: Redelegating to another validator does not impact your qualification for the "Staking Incentive for Long Term Token Holders" bonus.
Step 1: From the Sentinel wallet overview you scroll down to the current validator you are staking to and click the letter “R”.
Step 2: Look up the new validators operator address. This can be found on the blockchain explorer by looking up the new validator.
Step 3: Enter the operator address and amount you want to redelegate. Leave the memo empty. Click “Delegate”.
You will now see the redelegation transaction confirmation message. This means you have successfully redelegated to the new validator.