You define the properties of a part through sections.
After you create a section, you can use one of the following two
methods to assign the section to the part in the current viewport:
You can simply select the region from the part and assign the section
to the selected region.
You can use the
Set toolset
to create a homogeneous set containing the region and assign the section to the
set.
For the frame model you will create a single truss section that you will
assign to the frame by selecting the frame from the viewport. The section will
refer to the material Steel that you just
created as well as define the cross-sectional area of the frame
members.