When someone settles, they make a place their home and live there. Settles can also mean when something goes down to the bottom, like sand in water.
If someone settles in a place, it usually means they are happy and comfortable there. When something settles to the bottom, it just means it goes down.
Examples:
She settles in the new house.
The dust settles on the table.
He settles in the big chair.
The cat settles on the soft bed.
The snow settles on the ground.
The boat settles in the water.