CMS Images not showing in 'Get Images From drop-down'

Hello all, this is my first post on the forum and I’m relatively new to webflow having only been using it for a few weeks.

I’m currently working out CMS as I know it is a very useful function.

The issue I’m having is that I want to make a lightbox or image grid for images from a CMS Project. I have a field for ‘Multi-Images’ but for some reason this isn’t a selectable option. Sorry If i have explained this poorly, hopefully the images bellow give a bit more context. thanks!

Here is my public share link