Open imToken COSMOS wallet and click on Staking button on the top of the Assets page to enter the Staking interface.  You can see the Withdrawal and Reinvest button in this page. Withdrawal means you can get all rewards from the staking. Reinvest means you can put the rewards to delegate again.

Withdrawal

Click on Withdrawal button, view the details then click Next and enter the wallet transaction password to confirm.

Reinvest

Click on Reinvest button, view the details then click Next and enter the wallet transaction password to confirm.