You must be registered as a Test Applicant before you can book a Test.
Applicants must be at least 10 years old. Younger children can only join Mensa using results from an IQ test from a Psychologist

Click on the Yellow [Registration] button on the right of the menu bar to create an account, register as a Test Applicant and pay the registration fee.

You can then return to this screen to book a test

Pending tests can not be booked at this time. Closed tests can no longer be booked, even though they have yet to take place.