To Playback the footage from your SD card, log in to the YI Home or Kami Home app.  On the Home screen, click inside your camera thumbnail to go into the "Live" view.  Click inside the "Live" view on the top half of the screen.  A timeline will appear.  The orange stripes are the clips of the footage.  Drag the orange stripe to a point inside the white vertical line.  At the top, "Live" will change to "Playback" letting you know you are watching the footage from the SD card. 

If you have inserted the SD card, but there is no timeline available for playback, please make sure the card is formatted.  To verify, click on Settings in the bottom right corner or select the gear symbol in the upper right corner.  Scroll down to the bottom and select MicroSD card under Storage.  Click on Format Storage Card.  Select ok to format the card.