Dynamic Grid - Lightbox setup

Make sure the image URL is select for the "LINK" field of the Dynamic Content item of the "Grid":
GRID > Content > ITEMS > [Articles] > Content > LINK > Dynamic > Article: Intro Image.

Then edit the "Grid" itself, click on the tab "Settings" and apply the following:
LIGHTBOX > Lightbox:  Enable lightbox gallery.
PANEL > Link:  Link panel.

Optionally remove the content from the field Settings > LINK > Text — unless you want to get a button.