It's a function of markdown formatting, you enter it like a link: [Descriptive Text](<a href="https://s3.amazonaws.com/files.d20.io/images/63594597/lw8tOFc6DF4C6bbjNTmaig/thumb.png?1538006932" rel="nofollow">https://s3.amazonaws.com/files.d20.io/images/63594597/lw8tOFc6DF4C6bbjNTmaig/thumb.png?1538006932</a>) However, as that link is currently set up, it will just be a hyperlink to take you to the image. In order to do an image insert the link must end in a supported image tag (.gif, .png., or .jpg), which you can do by either deleting the ?#####... at the end, or add an image tag to the end (e.g. #.png): [Descriptive Text](<a href="https://s3.amazonaws.com/files.d20.io/images/63594597/lw8tOFc6DF4C6bbjNTmaig/thumb.png?1538006932#.png" rel="nofollow">https://s3.amazonaws.com/files.d20.io/images/63594597/lw8tOFc6DF4C6bbjNTmaig/thumb.png?1538006932#.png</a>)
OR
[Descriptive Text](<a href="https://s3.amazonaws.com/files.d20.io/images/63594597/lw8tOFc6DF4C6bbjNTmaig/thumb.png" rel="nofollow">https://s3.amazonaws.com/files.d20.io/images/63594597/lw8tOFc6DF4C6bbjNTmaig/thumb.png</a>) Either one will give the same result, but the #.png method is useful when referencing an image url that doesn't have the image type contained in it. You can do this for PNG's, JPG's, or GIF's.