I've created an account with WPMUDEV, bought Appointments+,

I've created an account with WPMUDEV, bought Appointments+, after using the free version.
Saw there where translations, also Dutch.
But how do I activate the desired language. Dutch in my case.

My WP site is in Dutch, except for the Appointments+ page, which is in English.
Thanks in Advance.

Arjan van der Vliet