Complex sentence: After they get inside, another officer arrives to fit Marnie's ankle bracelet telling her she cannot move more than from the detector in the hallway and if the alarm sounds for more than three minutes, the police will be notified.
Split into simpler sentences: After they get inside, another officer arrives to fit Marnie's ankle bracelet. He also tells Marnie that if the alarm sounds for more than three minutes, the police will be notified.