I used to use Solidworks (3D CAD software). I like solidworks because its what I learnt on (my company at the time used it). You could borrow a copy and teach yourself with lots of youtube tutorials .
Or there are free CAD programs all very good if you don't want to borrow stuff.
I highly recommend learning this in your free time. You can design something and then use a 3d printer?!?!
I used to get a set of drawings and with solidworks a cnc plasma cutter, cnc waterjet, Pressbrake and a breakpress I could cut, fold, bend and weld anything you wanted in any metal except cast. Good old days.