The FI9853EP has an on board microSD card slot that can accept up to 32GB cards for local on-camera recording. In order to install the microSD card, power down the camera and remove the main dome from the base and mount. Then firmly twist the dome pieces in the direction as if you were opening a jar of jam. Once open you will see the card slot on the main circuit board.
Be very careful as you can void the warranty if you damage internal components or cables.
When closing the camera, make sure the seal is in place, make sure the threads are properly aligned and not cross-threaded and then twist it tightly for a good seal to avoid moisture getting in to the camera.
See the attached PDF file for details and images.