expression, ichidan verb
settle down; make oneself at home; stay for a while
Literally 'settle one's hips'; used when someone stays in a place for an extended period, often implying they get comfortable and are not in a hurry to leave.
彼はソファに腰を落ち着けて、本を読み始めた。
He settled down on the sofa and started reading a book.
I was finally able to settle down in my new place.