If you have Momentum firmware on your Flipper Zero, then the apps are already on Apps/GPIO. Go to to get precompiled .fap files, or compile your own following this.
To prepare the board for uploading, jumper pin IO0 to GND and press and release reset on the ESP32CAM. Upload the firmware pressing Install button below. For more details on the apps check this video, or take a look of the documentation.Enjoy!