Filling out this form is straightforward. Fill out all of the required donor information. 8.Click "Donate Online". Full Name (Last, First, MI):. In this post, I'm breaking down how to write a donation letter. Time donation online with a credit card. Please spell check, include how you would like your name(s) signed, mention the amount if desired, and format your message as you would like it delivered. The letter should include: The letter should include: You may choose to designate your contributions for a County of Sacramento non-profit organization.