Annotating/marking photos using preview

• With an image open in Preview, go to the View menu and choose Customize Toolbar.
  
• In the window that appears, drag the Annotate button up onto your toolbar, then click Done.
  
• Now, the Annotate options in the Tools menu may be inactive, but the toolbar button still works.

• Just Click and hold on the Annotate button to bring up the different annotation options.
  
• Once you have selected your tool, just click and drag on the image to add the annotation.