The Xme functions are bound into the standard Motif library (typically stored in file libXm.a). Therefore, you do not need to bind your widget with any special libraries in order to call an Xme function. Similarly, you do not need a Motif source license in order to call an Xme function.
You call an Xme function just as you would call any Xm convenience function. That is, you must include the appropriate header file, and you must provide the correct type and number of arguments to the call. The reference pages in Chapter 17 detail the required information for each Xme function.