There are several ways, but this is simplest.
Imgur photo hosting is probably the easiest
1. Use a desktop or laptop computer. None of the apps allow you full access to the photo hosting site's capabilities.
2. Open an imgur.com free account
3. Upload image to imgur.com
4. Once the image has uploaded to imgur, right click on the image and "open link in new tab"
5. Copy the url of the new tab
6. enter the url in the same format as the the insert non floating image option here at TFF
7. be sure to add .png or .jpg at the end of the url if not already on there.