Multiframe has an origin for its coordinate system indicated by a symbol of x, y and z axes drawn in the Frame window.  You can control the display of these axes by using the Axes command from the View Menu.

You can also change the location of the origin, relative to a structure.

§    Choose Move … from the Geometry menu

A dialog box will appear allowing you to enter x, y and z coordinates for the new position of the origin.

This command is useful for creating structures that are made up of larger sub-structures. You can shift the origin to a convenient location prior to doing the drawing for each sub-structure.