Click and drag the bottom right corner, between the chart and the green border.
A massive thank you to Jonathan Alexander who emailed me this:
Add the following in a script in the head section of your page:
The DIV1 variable needs to be changed to the id or your holder div in the next step.
Add a div to encase the open-flash-chart div. Give it some padding so you'll have something to grab on to.
Make sure your open-flash-chart parameters for height and width are set to 100%.
When you download mootools, make sure you get: