Tick anything you already have, in any order. Quests unlock once this is done.
You request an address, send a card, and a card comes back to you from somewhere else entirely. The whole system is free apart from postage.
Open Postcrossing2 things left above. Quests are real things you go and do, so they only make sense once you have what you need.
First one waiting: Send your first card and register the ID