I am currently playing with Kookaburra with the aim of, initially transfering my pangolin site over.
In Pangolin I use masthead images on all may albums and album sets, defined in the template. However I cannot see this anymore. So I was going to use Hero images, but how do I
Are you referring to masthead images in the Kookaburra page template?
That is found in the Header section > Display Header Primary, under Add Logo Image
Thanks that the one, I had not expanded the Display Header primary. Basically it does the same as Masthead in pangolin.
Still finding my way round.
Me too! 
To answer the initial questions about hero images, these are set on a per-album basis.
To set, edit an album.
You can either upload an image, or open the large view of an image in the album, then select it as the hero image.
This video walks you through the process, used for setting thumbnails and hero images both.
