Click on the Purlin icon from the ribbon menu .
The steel purlin toolbar will open.
Click the profile list in the steel purlin toolbar and select a profile from the list.
Choose the first of the steel beams that will form between the steel purlins.
Once you have selected your second steel beam, the steel purlin settings dialog will open.
The dialogue includes parameters such as the number of purlins, layout, joint features, etc. Click the OK button after making the settings.
Purlins will be formed.