You can access the Dial-in page editing tools from the left sidebar under Live → Teleconference settings.
Under Dial-in Registration Settings, you will find a button called Edit Dial-in Page, which opens the page editor.
These settings allow you to control how users register via the Dial-in page:
Require email field in dial-in registration
Requires every user registering through the Dial-in page to provide an email address.
Send as calendar invitation
Sends a calendar invitation to the user if they provided an email address.
Disable sending dial-in registration email
Prevents the system from sending the automatic registration email.
In this section, you also have access to the theme color settings for customizing the Dial-in page appearance.