In order to do this you have to limit the access by using a permission scheme that allows your users to browse the project, but only admins can do anything else. It is a fairly simple change, I would recommend that you use the role Administrators instead of a group, that way you can control how have more permissions in the project by adding them as a project admin.
You must be a registered user to add a comment. If you've already registered, sign in. Otherwise, register and sign in.