To zoom in and out on a chart simply click and hold the left grey slider bar just below the chart. Moving the bar to the right will zoom in and moving it to the left will zoom out.
Your chart perspective can also be changed by clicking and holding over the vertical column to the right of the chart and then dragging your cursor up and down. This will expand or compress the price bars on the chart.
To scroll up and down the price axis right click in the same place and drag your cursor up and down.
You may also display different sections of the price history by moving the right grey sliding bar. When this is done three red bars will appear inside the sliding bars. This will notify you that you are not seeing the most current and updating price.
To see this demonstrated in a video, click here.