指示 (zhǐ shì) is a formal word for 'to instruct' or 'to indicate', used in official or workplace contexts when a superior gives a directive or a device shows data. It is more authoritative than 指出 (zhǐ chū 'to point out'), which simply draws attention to a fact, and more formal than 吩咐 (fēn fù 'to tell someone to do something'), which is everyday spoken instruction.