You cannot reverse the direction of your camera.
The camera is mainly there to allow for video "skyping" or chatting, so whoever you're skyping with can see you.
The camera app does allow for single pictures to be taken but it can only take what it can "see" and it can only see from the front of the Tab, where the lens is. There is no camera lens on the back of the Tab.
If you wish to take pictures away from you , you either have to turn the Tab around, peer around at the display (with the camera app running) and see what is displayed on the screen and take the picture. Alternatively, you can have your back to the scene that you wish to photograph, move the Tab until the picture that you want is on display,( and you aren't in the picture) then take the picture.
As you can see it is not really meant for taking pictures like a camera. Best example is to liken it to mobile phones, the ones you get with front camera only (good for selfies and video chat) and the ones you get with front and back cameras ( good for selfies, video chat and as a replacement camera saving the need to carry both phone and camera). Yours is like the front camera only phone.