Like in the theme preview screenshot?
We created that using the WordPress gallery shortcode
https://codex.wordpress.org/Gallery_Shortcode
to display those images.
e.g. add shortcode in your page, where the ids are the IDs of the images you want to display
[gallery size="large" link="none" ids="1851,1852,1847"]
if you wanted 4 columns it would be something like
[gallery columns="4" size="large" link="none" ids="1851,1852,1847,1848"]