After you have delegated your tokens to a validator, be aware that unbonding your INJ tokens and having them returned to your Injective Network wallet balance is not instant. Injective's UnbondingTime is 1 day (24 hours). If you decide to withdraw tokens from a validator you will have to wait for 1 day until your unbonded INJ tokens are returned to your Injective Chain INJ balance on the Wallet page.
Open the Validators page by clicking Validators from the top menu bar.
Find a validator from the Validators list who you would like to delegate your INJ to. In the same row under Actions, click the Delegate button.
This will open up a modal where you can enter the amount of INJ to delegate to this validator. Enter the amount and click Delegate.
This will open metamask with a transaction for you to sign. Sign the transaction and wait a few moments.
When the modal closes, return back to the Wallet page to confirm that the Delegations table reflects delegations you have made to validators.