For Reolink Lumus, you can insert a micro SD card (up to 128GB ) into the camera for video recording. Below is a guide on how to install the SD card for Lumus.

Step 1. Power off your camera. Open the rubber cover on the SD card slot.

Step 2. Insert a micro SD card (with the pin side down as shown in the picture below) into the SD card slot. Use a paperclip or your fingernail to push it in until you hear a slight click sound and the SD  card does not pop out.

Step 3. Put back the rubber cover in place and power on the camera.

Here is a picture showing where the SD card slot is on the camera: