I don’t think the importance of exposure could be overstated as an element of photographic composition
If you put all of your effort into framing and all of the other elements of composition and you miss the mark on your exposure, all of your other efforts are diminished because the tonality of your picture is too bright or too dark.
Once you learn how to consistently get the exposure that you want you’re well on your way to getting the photographs that you want.
The following links will take you to classes that will help you with exposure.