First, insert the battery and/or turn on the drone. Second, make sure that there is a red or green light at the bottom of the camera if it is removable. If there's no light, remove the camera and reattach it to the body. The lens should be pointing towards the same direction as the front of the drone.
Make sure to use a 16GB Micro SD Card or lower. Format first before use.
If this does not solve the issue, please contact customer service.