To enable the "CASH" option for Donor Pledges / Pending Donations in the Participant HQ:
  1. Go to Communities > Special Events > Friends Asking Friends > Kintera Thon
  2. Find the event
  3. Hover over the event name and select Website Info
  4. Click Website Features
  5. Scroll down the page and find the section labeled Pledge Entry Tool
  6. Put a check by "Add cash option to pending donation"
  7. Save
  8. Go back to the Website Information Checklist and click the green Publish this Event Now button.
Now the option to select "CASH" will be present from the dropdown when entering donor pledges in the Participant HQ.