Lasernigel,
FS inbuilt ATC works with any aircraft that you have or can download.
To activate the ATC all you need is a key to open the ATC window. From memory(I don't use inbuilt ATC that much) I think it's the ` key. If not, you can go to your options menu, then assignments and assign a key to open the ATC window.
Also, remember to also activate dynamic scenery in the display menu and in the ATC menu bring up your traffic percent. Otherwise, it'll be a bit loney up there
Cheers!
PS... as others have said, there is so much more to flying FS than flying stand alone. There's a huge online community, supplying just multiplayer or multiplayer with ATC(Not computer generated and over voice aswell). If you need any info, just ask.