You can make a donation field required by following this path in Luminate Online:

  1. Fundraising >  select Donation Management
  2. Click the All Donation Forms tab
  3. Find the form you want to change and click "Edit"
  4. On 3. Design Donor Screens click Edit next to Donation Form
  5. Select the data element that you would like to edit (from the list on the right, within the gray box at the top of the page)
  6. Click Save Order and Edit Selected
  7. Mark the box next to "Yes, this field is required."