Let's assume we want to allow just one person, the club secretary, to manage and update contact details. This means we need to create a specific group of users who can access the backend, but who aren't able to view or change anything other than the Contacts menu and functionality. The steps are as follows:
Go to Users | Groups and click on New to create a new group called Contact Administrator.
Set the Group Parent to Registered. This way, the new group gets the login permission from the Registered group, but no other permissions.
Click on Save & Close to apply changes.