That usually means there’s excess moisture in the fridge and it’s condensing and freezing on the fins. A light layer of frost is normal. But if they’re heavily frosted or iced over, you’ll want to defrost them
Turn off the fridge (or switch it to OFF on the control panel)
Open the doors
Let the frost melt naturally, or speed it up with a warm cloth
Wipe up the water
Dry out the interior: Moisture buildup usually comes from warm air getting inside, like when the fridge is opened often or loaded with warm food. Keeping it closed as much as possible helps.
Check the door seals: Make sure the gaskets are sealing tightly. A bad seal can let in moist air.