Click Pop-up Windows on the left.
If you don’t see Pop-up Windows, be sure to scroll to the bottom of the list.
If there are websites listed under Configured Websites, and you want to change the setting for these sites (for example, they’re set to Allow, but you want to change them to Block), select each website, then click Remove.
If you don’t see Configured Websites, either you haven’t set pop-up blocking preferences for any sites yet, or you’ve cleared the list.
Click the “When visiting other websites” pop-up menu, then choose one of the following:
Allow: Pop-ups for the websites appear.
Block and Notify: Pop-ups for the website don’t appear, but when you visit a website with blocked pop-ups, you can choose to show them.
Block: Pop-ups for the websites don’t appear.
If you block pop-ups on a website, but you continue to see pop-ups on the website, you might have unwanted software on your Mac. See the Apple Support article Use Private Browsing in Safari on Mac