Most great authors are also great readers.
Find books which cover similar time spands and see how the narration was dealt with in them. Use what you like and avoid things you don't. Or reread what you have written or re-analyze what you know you want to write and try to think what situations would foreshadow a scene. Four years is a long time, but if you are focusing on a particular event which happened over the course of those years, you could 'skip' several months at a time and still have a coherent story. I m in great need of some advice.