Here's the answer I was looking for.

SimpleGallery and Engage:Publish need to be installed.

A test article in a page called "News" where E:P is installed

A test gallery called "News Images" with some demo images.

Select the DropDown Menu > Settings options from the E:P module on the "News" page.

Select the Advanced Settings then click on Configure beside "Allow items from other lists to display here"

Then select "Article Display Settings" and check the box next to "Display Thumbnails from Photo Gallery " and set your settings.

Go back to the DropDown Menu on the E:P module and select "Manage Content". Select "Edit" beside your test article.

Go to "Extended Properties (Click to expand)" and above the "Display Options" you should see "Photo Album" with a dropdown list of the availabe galleries from SimpleGallery.

So simple when you know !