Whether you can start over yourself depends on how far you've got.
You haven't finished yet (you haven't clicked Agree and submit)
In WeTicket, go to Settings > Payments.
You'll see the message "Payments not active, action required" and the buttons Continue setup and Reset.
Click Reset and confirm. Everything you filled in is deleted. This can't be undone.
Click Set up Payments and start again.
You've already finished (you see "Ready to accept payments")
You can always change your legal form. We've got an article on that here.
Just a typo in your details? Then you don't need to start over. Contact us and we'll work out together how to fix it.