To be using money i assume you have some sort of fleet. So 1st go to Manage Fleet and get rid of ships from there(if you are out of dp this will leave you defenseless) Assuming you have had some guidance or following the missions you are probably a commercial terran. As long as you have no fleet and are not in debt you should have a positive income.
To increase the income you need to do more research and/or get more land and build more commercial