Since the picture resource consists of a series of commands instead of a bitmap, you need a way to move around to different points. Any drawing commands you do are added to that particular spot in the picture.
The quickest and most obvious way is to use the slider bar at the bottom of the screen. It shows the current position, and lets you instantly move to another position.
You can also click on a command in the right-hand pane, and the picture will move to that point. A thin green line reminds you exactly where you are positioned.
When your picture gets big and complex, it can often be difficult to quickly narrow
in to a particular position. If you need to go to the spot where a pixel last changed
its colour, the history tool will do that. Left-clicking on a part of the pic will bring
you to the point just before that pixel changed colour. Right-clicking will bring you
just after.
Use the zoom tool to zoom in (left-click) or zoom out (right-click) on the pic. You
can also use SHIFT-mouse wheel, or CTRL-minus and CTRL-plus.