We want to create accurate, working things rather than nice pieces of art, so we will use AutoDesk's Inventor software. You can get a free student licence for this fantastic software by checking out the CAD section of this site. There are also links to a huge video tutorial series that will show you how to create a scooter in Inventor.
Below are videos that show you the real basics that will enable you to start using Inventor to create your designs.
This video shows you how to set up Inventor, create your first part - a cube, and then save it. Make sure you have these basics sorted as everything else you build in Inventor will rely on these skills.