If you're an artist, I can't help you. ;-)

If you're into engineering design, see if you can grab a student license via your college. Bassna mentioned Solidworks, there's also CATIA. They are great. Plus, you can find countless websites of engineering teachers putting their lessons online and that'll get you through the beginning. Once you're past what they can provide, you're entering the semi pro level and you'll need an actual training. My advice : practice.