How do i set the self timer on a canon sd850 is?

With the camera in the shooting mode, press the bottom of the multicontroller. You should see a set of icons displayed vertically on your LCD, with a square at the top and a couple of circles with a 2 and a 10. Press the bottom of the controller again to highlight either the circle with the 2 (2 second delay) or the circle with the 10 (10 second delay). Press the Set button to select. To return to normal shooting mode, repeat the process but select the square at the top.