You can view a complete list of all tickets past and present opened by any given client. This is done by navigating to the Client's record and clicking Tickets. Using the view profiles you can choose to view different sets of tickets, be it Open, Open and On Hold, or Closed, or even with given statuses like those awaiting approval.
Viewing the Site record from a ticket
On the right hand pane or the details tab, click into the site's name to bring up their record:
Viewing the Client's record from the Customer's Screen
Click on the customer tab in the navigation pane and find the customer you wish to view and click on their name or row. Then navigating to the "Sites and Users" tab, click on the Site you wish to view.
The Ticket Screen
However you navigate to this screen, the tickets tab will always be in the same position and display the same information. This ticket screen acts the same as the main one only with the restriction that you can only view the tickets for this Client.