Steps

1. Click on modules in the main Drupal menu <http://mysite.ucsf.edu/admin/modules>
2. Make sure the diff module is on
   • If it isn't on, check the box for diff, and then go to the far bottom left of the page and click Save Configuration
3. Go to Structure--> Content types -->Basic Page in the menu <http://mysite.ucsf.edu/admin/structure/types/manage/page>
4. Find  the "Publishing Options" tab on the bottom of the left of the page and click
5. Select "Create new revision"
6. Click Save Content Type.
7. Go back to Structure--> Content types -->Basic Page in the menu <http://mysite.ucsf.edu/admin/structure/types/manage/page>
8. Find the "Compare Revisions" tab on the bottom of the left of the page and click
9. You should now see two check boxes Show View changes button on node edit form and Enable the Revisions page for this content type. Check both boxes
10. Click Save Content Type.
11. Go to one of your pages and make a small edit on the page to test
12. That should do it.