by default you should have a sim tray with room for just a sim and one that's slightly bigger. you'll need to place your SD card in the second slot.
if you have a different tray it could be a replacement from a different model.
to clarify. you can only use 1 sim and SD OR 2 sims.
if you want external storage AND 2 sims you will need to invest in a OTG adapter if you don't have one and use a sd card reader or compatible USB stick to hold your sd card.
