I know it must be stupid simple but I cannot figure out how to copy and paste stuff. Please help!
What exactly do you want to do? You can select an object, right click on it, select Copy at the top of the Context menu, then right click out in a blank part of the model and select Paste from the Context menu. You could also use the standard keyboard shortcuts for Copy and Paste. Probably more useful is to activate the Copy function of the Move tool and drag a copy in the desired direction and enter the desired distance.
What are you modeling?
You should go through the instructional materials at learn.sketchup.com
Doh! I knew that! Thank you for your help!