All your indoor plants will require food one year after purchase. The nutrients in their fresh soil will deplete naturally over time so a top up is needed to ensure healthy growth and no yellowing leaves. Sometimes the addition of food will also mean you don't have to repot so quickly.
Simply add 5ml of this liquid feed to 1 litre of water, and get watering! If you can do this at least once a month during the growing season (March - September), your plants will love you for it!