Hello Melissa.
After recording your sounds on Audacity, click on "Effects" on the menu bar and look for "Click removal" and "Noise reduction".
They are not perfect, but help a lot although the noise reduction process needs a bit of experimenting to find the best result. You won't be able to remove the crackle (if at all) without losing the clicks, too
As for clarity of vocals: probably not much you can do about that.
Hope that helps a bit.
Keith