Fo is on the fourth stratum of rock on Dinosaur Mountain. There are four prominent 'tooth' like rocks. Fum is the highest of these and directly south of Dum, the highest rock on Dinosuar Mountain. Fo is just south of Fum. Fi and Fee are south of Fo.
Getting There
Follow the Mallory cave trail and turn off at the gully between the Finger Flatiron and the Box, just past Der Zerkle and before Mallory Cave. Hike up the gully and then around the west side of the Finger Flatiron. Fo is right across the gully from the west face of the Finger Flatiron.
Another way to the west side of the Finger Flatiron would be to climb the Hand (5.4) or the Finger Flatiron (5.7s).