This is a three part process. First you prepare the medicine, then you capture your bird, and then you administer the medicine. To read more go to: Capturing Your Bird and Administrating Medicine and Supplements.
Because one wants to keep the experience as pleasant and unstressful as possible, before capturing your bird, lay out all the materials you will need; in this case, medication, already drawn up in the syringe and the proper size towel for holding the bird. Always follow the prescribed dosage and recommended method of administering medicine.