Hi Gloria: My experimentation imples that the direction in which you draw a line (if using "weldment" functionality to later represent a structural member) sets the FEA BEAM axes direction. That is, if you draw left to right, you get different axes directions compared to drawing from right to left.
If you extruded a cross section sketch to make a structural member, the FEA BEAM axes direction appears to be set by the extrusion direction. In the Simulation tree, you can right click on the results icon for the shear or moment diagram, choose "settings", and check the option to show beam axes on-screen. There is a little video we did at GoEngineer's YouTube channel, illustrating how to show the beam axes direction and how they relate to the S/M Diagrams. Hope this helps a little - Tony
SolidWorks Simulation - Beam Shear & Moment Diagrams