Explanation

In and Into

In = (Located inside or within)

Into = (Indicates entry or insertion)

The girl jumped into the sea.

They were sitting in the room means وہ کمرے میں بیٹھے ہوئے تھے

Note: “Into” is not used with “Enter” as the sentence becomes superfluous.

She entered into the room.

The boy threw the ball into the well.