When using the image feature, you need to have the link address and not the actual image.
1. Right click your desired image and click "Copy Image Address" as shown in the image;
2. When uploading the image, it must end in ".png", or ".jpg",".gif" etc. As shown below;
3. Once you've click insert, the image should show.
If you have any more problems relating to this topic, message me via conversations and I'd be happy to help.