Simply drag the picture from the grid view to it's new location in the folder panel.
You need to have a folder selected as source for the grid view and not a collection or alike.
What exactly is it that is not working? Any messages?
In the Library grid, make sure you click-n-drag on the image, not the gray frame around it.
The problem was between the flatscreen and the chair...:-) I clicked always on the gray frame around and not in the image.
Now it works!