We recommend you use your Event Manager app available for iPads. You can also sell tickets using a computer, but be aware, that this solution is not updated as often as our Event Manager app.
You can find the web version here (UK Version)
Alternatively, to sell tickets through computer simply go to My Events → Manage on your event and on the left hand side clicking On Site then Billetto App. Scroll down and you will find the below options. Choose 'Open in browser' to sell tickets via a computer.