Grid is so Not easy to use (Copy Paste into grid, why not?)

I have been trying everything, but I can't just Copy and paste an image into a grid; why not?
Why can't I drag an image into the grid? 
Why, also, when I go to replace an image in the grid, it does not have the option to view photos and images I have uploaded already? 

The workflow is so bad. 
- Make grid
- Download my images from online
- Go to the grid
- Click on grid
- Remove the image in grid square
- Click add image
- find an image on my desktop
- Upload

I would love to copy an image from my photo site online, paste it into a doc, and then drag and drop it into a grid; why make the grid tool feel so cumbersome to use?  😞 

Amy I just not seeing the option to easy add my images to the grid?