How do I add a group to permissions? I can't seem to find this option anywhere.

Searching in the box only does members and I can't seem to find it in the group moderator permissions?

 

Thanks in advance.

The answer is in your image, above the SAVE button. 

It's not the answer, please read my post, that's how to add INDIVIDUAL MEMBERS. Not groups like "Admin" is currently, seen highlighted.

Admin CP > Groups > whichever group you want to permit > Content > Social Media Promotion toggle ON