OAS Application consists of two parts as explained in . After the library and the config files are placed in suitable places one can start OAS.
OAS binary accepts one argument that is config file name. It logs all the errors to stderr, which can be suitably redirected to a file.
One instance of OAS runs one application. There can be multiple instances of OAS running on same machine, which hosts different applications. Even multiple instances of same application can be run as long as they listen to different Unix domain socket.
The Unix domain sockets OAS uses are placed in cgi-bin directory of the web server. This is the convention that must be followed to maintain communication between web-server and OAS.