Users who you have added to your Contact list are considered "Contacts." In the
File->Preferences->Contact Approval menu you can choose to accept incoming messages only from Contacts.

When another user wants to add you to his/her Contact List, you will get an authorization request pop-up dialog box. If you accept the request, the user is authorized. If you decline the request, the user will not be authorized. There is also an Ignore button on the dialog box. If you ignore the request, any further messages from this person will not reach you.

If you block a user, he/she will no longer be able to communicate with you (and vice versa). You will always appear offline to the users you have blocked. You can edit the list of blocked users under the File->Preferences->Ignore List. As another option, you can block somebody in a dialog by clicking the Ignore button or, choose the contact and click menu Contacts ->Manage Contacts -> Ignore Contacts.

If you want to add a contact, simply click "Add a Contact" from the Contacts menu and enter the contact's Member ID.

To delete a contact, select the contact and right click. Then click "Delete Contact from Group."

To permanently delete the contact, click "Delete Contact from Contact List."

To move a contact to another group, select the contact, click "Move to Group" and then, from the drop-down menu, specify the group to which you want to move this contact. To copy a contact to another group, click "Copy to Group" and perform the same action.

To manage your groups, simply choose one of the following options from the right-click menu: Delete Group, Create New Group, Rename Group.

Note: you are required to remove all contacts in a group before deleting a group.

Right click the contact in the Contact List and select "Edit Contact Details," and specify in the pop-up box how you want this person to appear in your Contact List.