Go to "Preferences" and select Print & Scanner with the scanner turned on. The scanner icon should (?) appear. Select it, if the window opens,it may look a bit different, kind of greyed out. I clicked on the bottom menu selections, choosing Pictures and and then Scan. I can't insert a screen shot because my hotoshop no longer works with Mountain Lion.
You also might try downloading an updated driver by selecting the "Apple" icon and selecting "Software Update".