[Jay O'Donnell]

Before you get to CAD, take some time to learn about all of the parts of an FRC robot and how they interact. Learn about how much power you want from your motors (so you know how many to put in) and then learn about gearing. Look through the different available gearboxes, figure out what type of frame you want to design (this is based on your team's resources) and then draw it out on paper.

If you have more specific questions that would be a good starting point.