WPMUDEV installation

Hi!

I've no idea how this works and I'm just getting started. I have four domains that I would like to have on a the same WordPress dashboard, however, I don't currently have a WordPress site plan for any of them. What are the first steps here?

Do I have to purchase wordpress itself from : https://wordpress.com/pricing/ and add one of my domains from go daddy first and THEN I can use YOUR plugin?

Thanks!