Signing in
A code by email, no password, and where your account comes from in the first place.
There is no password
Arvald does not give players passwords. You enter your email address, a six-digit code arrives, you type it in. That is the whole sign-in, every time.
Nothing to remember, nothing to reset, and nothing worth stealing from a list of ours.
Your account appears the first time you sign in
There is no sign-up step, and nothing to fill in. The first time you sign in with an address you have booked with, the account is created around the bookings you already have.
That is also the limit of it: an account can only be created for an address that has booked through Arvald online. If you enter an address that has never booked, you get the same screen and the same wording, and no code arrives. That is deliberate, so this form cannot be used to work out who does and does not have an account.
A booking your coach entered for you by hand does not count here, because the address on it was typed by them rather than by you.
What you can and cannot change
You can sign in, see your bookings and cancel them.
You cannot change the name on your account yet. When the account is created, the name is guessed from your email address, so it may well be wrong or odd looking. It is only shown to you; your coach sees the name you gave them when you booked.