this expression refers to one`s desire to grow either professionally or personally speaking; no matter what it takes if you really wnat to acomplish a personal goal, you can do it.
Lucy: I wish I colud be a Doctor, but university is really far from where I live, and I have so many limitations!!
David: Hey, remember where there is a will, there is a way!
if you really want that, try hard and you will make dreams come true.