For organisers
Tickets and places
How many places there are, the kinds of ticket, supported places, and extras.
Places
Places is how many people can come in all. Every kind of ticket draws on the same count, so you can't sell more places than you have, however the tickets are split. Set it before booking opens. Most tickets in one booking stops one person booking the whole event.
Ticket types
Under Ticket types, press Add a ticket type and give it a name and a price: Standard, Day ticket, Under 18s, whatever your event needs. A ticket can be free. Give one its own limit if only some places can go that way.
Supported places
If you'd like people who can afford it to help others come, add a Supporter ticket (a little more than standard) and a Supported one (less). Each supporter ticket sold makes one supported place available, so the supported places are always paid for.
Pay what you like
For a sliding scale, switch a ticket's Pricing from Set price to Pay what you like, and give a Suggested price, a Minimum, and a Maximum if you want one. Bookers see the suggested price filled in, and can change it to anything in your range before they choose their tickets. A minimum of 0 lets people come for nothing. Everyone booked on that ticket in one booking pays the same price, and discount codes don't apply to it, since bookers already choose what they pay.
Extras
Things people can add to their booking that aren't places: an evening meal, a songbook, a parking space. Press Add an extra, give it a price and say how many there are; Tutti stops selling it when they're gone.