Your phone supports an optional microSD card up to 1 TB.
A Class 2, 4, or 6 card is sufficient.
Your phone uses the card as portable storage for media files: photos, videos, and music. Because it's portable, you can easily swap the card and its content between devices. After you insert the card, be sure to update settings within media apps (like camera, music, and podcast apps), so they use the card to store content you create or download.
You can't store apps on the SD card because it is portable storage.
Insert the SIM tool into the tray hole and gently push to pop it out.

Insert or remove the cards as needed.

Push the tray back into the phone.

What type of issue do you have?