Yes you can add credits at any point in the slideshow by using some of our slide template designs. We have a few templates called ‘End credits ....’ which may be of help even for the beginning of the slideshow.
To create a new slide from a template design,select 'Create slide from template' option which is a sub option in the 'Add pictures or video to slideshow' button (located bottom left just about storyboard). (see attach picture of end credits template)