If you want to add a picture to a letter or acknowledgement you should follow these steps.
Firstly the picture needs to be available on the internet - an easy way to do this is to use Dropbox - you can create a free Dropbox account and share a picture - see this for more info. From Dropbox copy the link to your picture.
Next in Donorfy go into settings and open the letter you want to add your picture to, press the image button - highlighted in yellow below - the image properties dialog will be shown - then
- Paste the Dropbox link to your picture into the URL field - e.g. https://www.dropbox.com/s/i6jqmgjt1wshdjhsa6/myimage.png
- Next add ?raw=1 to the end of the link -e.g. https://www.dropbox.com/s/i6jqmgjt1wshdjhsa6/myimage.png?raw=1
- you can optionally set the width and height of the picture
When you press OK your image will appear in your document.
Finally save your changes.
If you want to include a signature in a document you can create a scan of the signature and then upload the scan to Dropbox - include the scan as you would any other picture.