Microsoft Lumia How-To Manual page 2

With the cards installed, replace the battery (making sure
that the contacts are lined up with the body of the phone)
and then carefully replace the back cover, pressing it into
place all around the edges to ensure the back lines up with
the screen.
If you needed a new sim card, you will have received a triple
sim card pack. You'll need to pop out the appropriate sim
card that is needed for your Lumia
Microsoft Lumia uses a Micro sim card.