You have a lot of different users that access different folders in SharePoint and you want to organize them via groups.
The problem is, you need to create groups within SharePoint, not the regular Admin Centre.
Creating a group:
- Open up SharePoint Site
- Go into Docs
- Click on the cog in the upper right
- Click on Site permissions
- Advanced permissions setting
Setting up permissions:
- Make sure you’re in Classic Experience
- Drill down to the necessary folder
- Click on Share
- Click on Shared With
- Click on Advanced
- Click on Stop Inheriting Permissions
- Remove the necessary groups