Can't Load Jazz Standards into Jazzlab?

Hi, 
I've downloaded the most recent version of Jazzlab (love it!). 
I have also just downloaded (from the resources tab), the zip file of Jazz Standards. They are .sng file types. 
I'm using a Mac computer running Jazzlab. 
My computer doesn't let me load them in Jazzlab at all, it doesn't recognise Jazzlab as an appropriate file to use the tunes. 

Hope someone can help resolve my problem.
Thanks