To register go to the registration page.
From there, you can register with your Google, GSuite, Exchange, Outlook or iCloud account by clicking on the Google, iCloud or Microsoft buttons. This will create your account and also connect that calendar. You will also be able to add more calendars from "My Profile" -> "Integrations" page.
You can also register manually by manually entering your details. This will create your account, but it won't connect your calendars, which you need to have connect to schedule meetings. If you registered manually go to "My Profile" -> "Integrations" page and connect your calendars to start scheduling meetings.