When adding an image to your booking, use the second option: "Enter an Image URL"
Here is a recording of the process (no sound):
Here is the step by step process written below...
Go to the Pixabay website. https://pixabay.com/
Make sure to bypass any ads that show up at the top.
Click on the picture to open a larger size of the image
Right click on the picture
Choose "Copy Image Address" option
Paste the address on the AXUS side
Click the SELECT & CROP button
Click the SAVE button