There's a 'play' button. It's got a box with a blue "play" (>) arrow in it.
Canon labels the buttons in white to indicate what they do while shooting, and blue to indicate what those same buttons do when you're reviewing your shots. Press the play button a 2nd time to take it back out of review mode.
There's an "info" button which cycles through several things the LCD can display. With a photo displayed, press "info" several times while looking at a photo and it'll show you various information about that photo. Press it enough times and it'll return back to the original image.
BTW, the info button also works when you're NOT reviewing shots. Press it several times and you'll see it allows you to display several different things while shooting. btw, one of the choices is to display nothing at all... the screen goes black. If the screen is ever black, you're probably in that mode (that or the camera is powered off). Just press the info button again.