Forbidden You don't have permission to access /oc-admin/index.php on this server

Running OSClass
1) create package - osclass
2) add user domain to package
3) install osclass
4) login osclass admin and added custom page
5) when I try to add content to custom page being redirected to 403 Forbidden page :

Forbidden
You don't have permission to access /oc-admin/index.php on this server

Q. How to fix the above error

OK * SOLVED *
Used CWP File Mgr (Adv)
to change file "/oc-admin/index.php" from 644 to 755
and was able to add changes to custom page