When you have connected your tickets to your DreamHack Account, you will be presented with some options. One being to "View tickets"
Viewing tickets allows you to see your available ticket(s) and bring up the QR code & ticket ID for the ticket. This can be helpful to find out which ticket is which if you purchased many ticket.
It also displays which seat you selected for your ticket(s)
The QR code needs to be presented when checking in at the event.