Queues allow groups of users to manage a shared workload more effectively. A queue is a location where records can be routed to await processing by a group member. If the sharing model for all objects in the Queue is Public Read/Write/Transfer, you do not need to assign users to the queue, as all users already have access to the records for those objects.
To assign a user to a queue
Before you assign a user to a queue, you must add the user.To assign a user to a queue, refer to the standard Salesforce Help.
When you create a queue, Salesforce automatically creates a corresponding list view. You can now access the queue list view from the Cases, Leads, Service Contracts or custom object tabs. Only queue members and users above them in the role hierarchy have access to the queue list view depending on your sharing settings.
Set up lead or case assignment rules to automatically reassign ownership of leads and cases to the queue.