Permissions can be assigned from the Manage Groups [1] page.

Open the group editor window by clicking Edit [2] on the active group.

From there, view the permissions of the group by clicking on the Permissions [3] tab. From here, you will see a list of all the root level containers. Again, keep in mind that if you assign permissions at this level, users enrolled in that group will be able to view all the content within the nested root levelcontainers as well.

There is also an option at the top of the page for Platform Permissions. Permissions can be applied here which encompass the entire platform. For example, if you give the group the Content Viewer permission at the Platform Permission level, all the users in the group will be able to see all of the content that lives on the platform.