You will need to download The O2 app. Search ' The O2' on the App or Google Play store.
Your ticket will be a unique barcode which gets you into the arena quickly. When you approach the arena entrance please have your barcode ready to be scanned.
Download for iPhone The O2 Venue App on the App Store (apple.com)
Download for Android https://play.google.com/store/apps/details?id=com.livestyled.theo2&pcampaignid=web_share
These should be links that take you straight to the app store to download the app.
You can also access venue benefits including exclusive discounts and offers on food and drink plus fast-track collection lanes.