Just log into zap.stream and clock the (+) on the top right, it should take you to the page where your stream keys is. 
You may want to set zapstream up on desktop with an extensionif you want to keep your nsec safe. I don't think Amber for android is supported yet for mobile. 

 all right... I will try this tomorrow when I am not in bed on my phone... but basically I would be streaming from prism app on my phone and the key from zapstream what what makes the connection so I show up on the zapstream feed.  

 You got it!