Next to each camera source name is a small, blue camera icon.
Tap this icon, and the camera will switch to the front camera (the icon will flip directions when switching between cameras).
Keep in mind that if you switch between front and rear cameras while "Record On All Cameras" is enabled, Switcher Studio will temporarily stop capturing video for the camera you are reorienting and start a new video file. This will occur when you change orientation after Record + Broadcast has been enabled.
While Live, you can also tap the small blue camera flip icon at the top of your screen, next to the word “Sources”. This will also flip to the front camera, and back again
Here is a quick video tutorial to help you as well: