First guess is to use this command:
Code:startx
If that isn't it, I'd have to Google around for more info.
This info seems older, but it still may work. This info seems a bit more modern, but both of these may work.
If you are not very familiar with Linux, is there any particular reason you are starting with a server distro instead of something that is more user-friendly for beginners? I'm not sure, but I don't think MATE will be their desktop, unless you have installed it manually. We can find out after you get the desktop to load.
Cheers