First, open [DApp] – [Staking Tools]
Make sure you are in 'Stash account' mode, and click 'Unbond'
Enter the unbonding amount
After the unbonding period completed (for DOT is 28 days)
Switch to Controller account mode
Then you will see the 'Withdraw' button besides dismissed DOT, click the button and sign the transaction, then you will get these DOT to your balance.