creating a wrapper for 3rd party software

Question

I want to write a c# wrapper for a CAD (computer aided design) system. To do this, I will need to do system calls to run the CAD software, and use the CAD system API.  Although I can get the environment vars I need and so forth, I am not finding any documentation on how to actually make the call.  Something like :

system(allegro.exe) ;
or
`allegro.exe` ;

How do I do this in c# ?