To assign a Phone Book contact to one or multiple queues, hover over the Configuration icon in the Navigation bar and click on Phone book.
You can drag and drop individual contacts to the queues.
Alternatively, the Enable multi-select option allows you to assign multiple contacts to the queues. Check Enable multi-select to begin.
First select the contacts by clicking on them. The checkbox on the right allows you to select all at once. Then select the queues to assign them to. The queues can be filtered using the search box. Click Assign to assign the contacts to the queues.