The first place i would start is the Help file. If you would do a search of the help file or even google it there is a wealth of information to be had.
You will need to look at a couple of commands.
BeamAdd
ColumnAdd
These commands will add a structural style horizontally and vertically. Steel like everything else in MEP is based on a style. You will need to have a certain style in your drawing in order to represent the beam or column correctly. You can add styles to your current dwg by using the structural catalog. You can start the catalog dialog with the _AecsMemberCatalog command. Select the style you want and it will add it to your current drawing. You can create your own custom styles manually or by using the Structural style wizard accessed with the _AecsMemberStyleWizard.
Hopefully this will get you started drawing steel components in Autocad MEP.
