First use the rectangle command to draw a 1" square. Then there are two ways to get the wall thickness. The long way is to set guide lines .06 in from each side and then draw in the lines. The easy way is to use the offset command with .06 and it will draw all of the lines for you. The last step is to highlight the center and delete it. Now you have a 1x1x .06 wall tube cross section.
Have you downloaded sketchup make 2017? You should and then set up the toolbars like I have them in the screen shot I posted. I tried a bunch of different arrangements for the toolbars before finally settling on the layout posted. I found that layout to be the most convenient for me.
Another thing I did after using sketchup for awhile was to take each command and see what it did and how to use it. I wish I had done this to start with. I still reference my Sketchup for Dummies book whenever I haven't done something in awhile. Or when things don't seem to go the way I expected them to. And I can't overemphasis the need to break your drawing down into lots of groups. Each component should be in its own group. It makes life much easier.