How do I restrict user access to certain queues?

As a default, users can open tickets for any queue. You can also limit ticket creators (users) to submit tickets only for certain queues. To do this, you will have to put that user in a group, and then limit the group's access only to the desired queue.

Note, by default, users are not placed in a group, or are classified as "Individuals".

You can change a user's group by going to Admin Settings> Users. Search for the user in the search bar, and click on the pencil icon to edit that user. Click on Group and choose the selected group from the drop down.

Now that you have placed your user in a group, you will have to define which queues this group will have access to. To do this, go to Admin Settings> Queues Access Rights.

Click on change to define which queues the group should have access to. Note, unless changed, groups have access to all queues (default). You can also specify access for the 'Individuals' group, which is typically unregistered users or those that have not yet been associated with a group.