Use an SD or SDXC card with Mac
If your Mac has an SD (Secure Digital) or SDXC (SD extended capacity) card slot, you can use a card to import images from a digital camera or to store information.
If the card has been formatted by a digital camera, inserting the card into your Mac performs the same action as connecting the camera to your Mac.
Insert an SD card: With the card’s metal contacts facing down and pointing toward the computer, insert the card into the slot.
Eject an SD card: In the sidebar of a Finder window, select the card, then choose File > Eject. After the card’s icon disappears from the sidebar, remove the card from the slot.
If you see a message saying the card cannot be modified: The slider on the side of the card may be in the locked position. Remove the card, move the slider to the unlocked position, then insert the card again.
See the Apple Support article Use the SD and SDXC card slot on your Mac.