How is Boost loaded?

The below can be used to view all of the installations of Boost on a particular system, where this example uses Coeus.

$ module avail |& grep -i "boost"

General/boost/1.66.0/gcc-7.2.0

How is Boost invoked?

Boost is not invoked, it is external libraries, not an executable. To Use the boost libraries in a C++ program, simply load the module and include the headers in the file.