It is difficult to help because we don't know how the definitions or theorems work.
How do your notes define jump? I have seen it defined exactly as what you are asked to prove.
Have you proved that if $\displaystyle f$ is increasing on open interval $\displaystyle I$ then $\displaystyle f(x-)~\&~f(x+)$ (the left-hand limit and the right-hand limit) exist for $\displaystyle \forall x\in I~?$
If you have that theorem then apply it to this problem.
If not, try to prove it. Or post the theorems and definitions you have to use.