Hi,
MonoX has support for multiple applications based on the ASP.NET membership model and you can use the same database to host more than one application, you can read more about this
here.
Few web.config sections defines the application that will be used, try to find the applicationName attribute that contains the application in use. To get the SnFile for current application you will need to use the proper repository which is using the current application id to fetch the proper file, so basically every MonoX web site is one application and repository layer has built in application filtering so you don't need to do anything to get the proper file.
Let us know if you need more information regarding multi application support.
Regards