Great! You have your link with the access token, or you have scanned the QR code, and you're ready to create your user.
We have disabled self-registration, so your user is created here. This is a prvate server and not just anyone can join. It is by invitation only.
When you navigate to the link you should be presented with this screen

It shows that your invite (access token) has been accepted.
There are 3 required fields Username, Password, and Confirm Password.
Your chosen Display Name is optional. It will be your Username if left blank.
Username: Must be in lowercase only with a minimum of 5 alpha-numeric characters.
There is a maximum of 32, but, well I hope, it is never reached.
Password/Confirm Password: Must be between 8-12 characters and contain at least one uppercase character, one lowercase character, and at least one number.
Once you hit submit, if all goes as planned, you will/should see the following.

Time to install Element (if you have not already).