As an attendee you have access to the collaborative group whiteboard (provided the Current Presenter has unlocked the Group Whiteboard. and a personal whiteboard.
To access the whiteboard, tap on the “Whiteboard” icon found in the Attendee menu bar. When the Current Presenter unlocks the Group Whiteboard, you will receive a notification and the editing tools will appear in the bottom left corner of the Group Whiteboard.
To resize the whiteboard you can touch and drag the resize arrow or tap the resize icon in the top right corner.