On days when your plant requires fertilizer, the watering and fertilizing tasks are combined, and the watering schedule is adjusted to make sure you don't over or underwater. Therefore, when fertilizing, you should be diluting your liquid fertilizer in water so that you don’t burn the plant’s roots, and then pour this mixture into your plant pot as you would when watering. You can read more about this if you go to your plant's Info tab and then scroll down to 'Liquid Fertilizing'.