To access the playback, click on the 5th button on the left-hand menu (called timelapse). You will then be greeted with a screen that is similar to the one below.

The camera you are viewing can be changed by clicking on the name in the list at the bottom

To change the time you wish to view, simply drag the timeline on the right-hand side up 

(The blue line is what will play), you can also zoom into the timeline to see a more precise timeline.

Some cameras record only motion (highlighted in purple).

To download footage click the scissors tool in the bottom right corner and adjust accordingly