This can be done in the app and via campercontact.com.
Via the app:
To use the app, you must register the first time you use it. You will be guided through the registration process by filling in a short form.
Via the website:
Click on 'account' in the top right corner and then 'create account'. From there, you will be guided through the registration process, during which you will be asked to enter your email address, a username and a password, among other things.
Please note! You only need to create an account once. If you change devices, you can simply log in with the same email address and password. You cannot register a new account with an email address that is already in use.