How to make a 2d character move across the x axis and up the z axis?!?

Hello, I am trying to create a 2d Plaformer and i want the character to be able to move not across the X axis but up the Y axis also so it looks like the character is not only moving across the road but up the road also. I Dont even know how to start to do this so if you guys can help that would be wonderful!!!