Paper prototyping is the easiest way to start, no need for fancy tools, just use anything you have access to. If your favourite sketching notebook is not with you, use napkins from a coffee shop. Get resourceful and don’t get stuck on tools, just start creating your prototype on paper. Also, don’t use that lame excuse that you are bad at drawing. You don’t have to be! Just start sketching and after a few iterations you will notice that you are getting better and better.