In your wallet click on the lock icon on the bottom right. Then enter your password and check the box that says "open wallet for anonimisation and staking," or whatever the check box says.

Also, be sure to encrypt your wallet first.  Make sure you write down the password and secure it in multiple places (no phone pics or keeping it in an open text file on your phone or computer).  AFTER you encrypt your wallet the program will ask you to restart.  After the restart, NOW backup your wallet.dat file.  Why?  Whatever backup of your wallet you had before encrypting is unusable after you encrypt, so make sure to delete all old backups and make new ones.