To start using the Collaborate's whiteboard, open the Collaborate panel by clicking the purple button in the lower right corner of your session window. Choose the SHARE CONTENT tab, then click SHARE BLANK WHITEBOARD.

Now that you've started sharing a whiteboard, you've got a number of annotation tools available across the top of your session window. The arrow button is for selecting and moving objects, like text boxes or shapes, that you've already added to the whiteboard. The pointer button helps draw attention to your cursor. The pen tool is for writing (in the example below, we use a touchscreen to get neater shapes than one might get with a mouse), and the square tool can be used to draw rectangles, elipses, and straight lines. The text tool (T) can be used to drop in boxes of typed text. The eraser lets you clear the whole whiteboard. When a tool is selected that uses color (pen, shape, text), color options appear to the right of the tool section. These tools are available when sharing a file or image as well.

When you're done sharing the whiteboard, click the square button in the upper right.