Task: I want to add the first photo from Google Photos on the presentation's second slide using the Google Slides app. 
Steps:
click on the plus icon (add) at the top of the screen to add an image in the slide 
click on the image button (top third option ) from pop up window at bottom of the screen 
click on the first option ( From photos)  from the pop up window at the bottom of the screen
choose first photo from recent images options  at the screen 
choose first photo from recent images options  at the screen 
choose first photo from recent images options  at the screen