Exactly one Monitor must be instantiated somewhere in your architecture. By convention, the monitor-box is usually placed on the top-level diagram, perhaps off to the side or bottom. There are NO link-connections to the monitor-box. (It sits by itself.)
The Monitor performs some initializations and file operations, in a neutral/central place, that are essential to all the other Perf-Mod-Lib component models.
The Monitor model automatically includes parameters.sim and subroutines.sim. (In the past, you had to include these separately. Older models may need updating to avoid multiple inclusions.)
The parameters.sim and subroutines.sim files include the subroutines, data-structure definitions, and parameters needed by the component models.
Naturally, you must also include the models of the components you use, such as generic_pe.sim, lbus.sim, or generic_switch.sim. These should be included after monitor.sim, because they depend on the parameters.sim and subroutines.sim files.
See also: Core Performance Models User Documentation