If you have a single SIM phone, the SIM card and SD card slots are located behind the cover on the left side of the device. Pull the tray to remove it. The tray attached to the cover is for your SIM. The tray for the SD card remains in the device, this tray can be pulled out and the SD card inserted into the tray with the metal contacts facing up.
For dual SIM phones, the second SIM can be placed into the SD card tray instead of an SD card following the orientation displayed on the tray.