Where can I change the default edits for CSS?

If I add something like padding it automatically puts a space in between padding and the next things which would be 15px (or whatever amount). I want to change the default CSS settings to where it would remove that space. {padding:15px;} is what I want it to look like by default.

Any know how to do it?

you need to find that css file then you need to edit those. using simply padding will add space all around the text or graphic you need to specify which direction you want padding to work like if you want space on the top you can add padding-top: 15px