Shift-drag the systems away from each other.
Hold Shift, click on the pile-o-systems, drag away the one it grabs. Repeat until satisfied. Once the systems are more-or-less where you want them, switch to the "Sys Pos" (System Positions) sidebar. You can press the "Line Up" button to align the systems to an invisible grid - it's a little bit touchy, and may move systems in the opposite direction from the way you expect. Once satisfied, press "Save Positions" to save the map.
