From the page campaigns listing screen, click the thumbnail image for any of your pages.

In the campaign popup, switch to the settings tab.

Here you can change the SEO tags from the "SEO Settings" section, and the OG tags (used for link previews on social media) from the "Facebook Settings" section.

PS: After making any update to the Facebook tags, please make sure to go to https://developers.facebook.com/tools/debug/

Paste your page URL there, and click on "Debug", to make sure Facebook refreshes its cache and sees your new changes.

How to Edit SEO/Social/Facebook tags of my pages ?