Grant the external users a specific permission in Office 365 site

Simple How-To steps on grant the external users a specific permission in Office 365 site

1. Grant the external users a specific permission (not add to a group) directly, such as Read, at Team site level.

3. Go to the specific library permission settings page. Click Stop Inheriting Permissions.

4. Select the specific external user’s permission to this library that is inherited from the parent site, and click Remove User Permissions to remove his permission to this library.

After that, the external user cannot view or access this library when he access the team site via External Sharing.