1) Build a permission group - see HERE for instructions. When deciding on permissions for this group, select District/Building Content page permission (NOT the superuser permission).
2) Navigate to the content page that you would like this group to have permissions too.
3) Edit that content page and in the top left corner, you will see an Add Staff Permission button.
4) Here you will see the list of permission groups you have already built. Select the group you would like to provide permission too.