The present disclosure relates to a wireless communication system and, more particularly, to a method and an apparatus therefor, the method comprising the steps of: detecting an SSB in an unlicensed band, the SSB including an index related to a CORESET configuration; determining, on the basis of the index, an RB offset used for identifying the position of a CORESET frequency associated with the SSB; and monitoring the CORESET in the unlicensed band on the basis of the RB offset.