You can see the depth chart in the chart pane of the main trading window. To access it, click this icon in the lower right of the chart:

Where can I see the depth chart?

Doing so will bring up the depth chart within the chart pane.

Where can I see the depth chart?

Moving your mouse over various points of the chart will give you an indication of the volume and price represented.

Where can I see the depth chart?

If you wish, you may switch the depth chart to full screen by clicking the other icon in the lower right.