To enter the Screenshot mode, tap on a placed Photo Booth and tap on the camera icon of its Information Panel. 

In the Screenshot mode, you will be able to move the camera around like in your normal park by dragging to pan, pinching to zoom, and twisting to rotate.

To apply a filter and a frame, just tap on the filter menu and select your choice. You can still adjust the camera position with the frame on. 

Tap the aperture button when you are ready. You can then save your picture in your device (if access to device's media is authorized) or share it on Facebook.