Zooming In and Out
Rolling your mousewheel forward or back zooms the map towards or away from where you are pointing.
To zoom in, centered where you are clicking, doubleclick on the map (not a marker).
You can also zoom in and out by using the + and – on the left. + gets you closer, - pulls you away.
Moving Around
You can move the map in any direction by clicking on it and dragging your mouse while you keep your finger down.
You can also use the arrows on the round wheel at the top left to move up, down, right and left.