If you have selected Print-at-Home as your delivery option, you will need to print and take a physical copy of your tickets to the venue. You will not be able to show your tickets on your phone screen at the venue, as the barcode will need to be printed in order for venue staff to scan and validate your ticket.
Please note, if you have selected E-Ticket Mobile Delivery when booking on the Ticketmaster App, you do not need to print your digital ticket. The QR code can be scanned at the venue from the screen of your smartphone. By turning up the brightness on your phone screen you'll be able to scan your ticket quickly and easily, getting you into the venue faster.