Spacing between staffs

Please read the Handbook - it's there under Support. If you are still not capable of doing what you want then please attach the score and tell us what steps you have done and what has happened.

See https://musescore.org/en/handbook/3/breaks-and-spacers#spacers, Staff spacer fixed down
And/or https://musescore.org/en/handbook/3/layout-and-formatting#style-page

The space between staves depends on very many things - one of which being, do you mean individual staves within a system, or between systems? So we would need you to attach your score to understand the specific thing causing there to be more space than your wish. But most of the relevant settings are in Format / Style / Page as far as the overall spacing, and spacers from the palette can be used top override this for specific staves.