Two types of circling approaches - both available at night:
1. From an instrument approach that is not runway aligned (or from say a RWY 15 ILS, circle to land on 33) - when in the circling area and visual, carry out a circuit within the circling area to land on desired runway.
2. A visual approach - within 5NM, join the circuit to land on desired runway.
Different weather minima apply to both. Above is a precis for Australia - other countries may be different in what they allow.