What should i do for an eye infection for my four year old?

Take to an eye doc: Take him/her immediately to be seen by an ophthalmologist.

There are : Antibiotic eye drops / ointments available for children , you have to be sure it is not orbital cellulitis that needs intravenous antibiotics and hospitalization . Take your child to the pediatrician asap

Topical antibiotics: If you child has signs of bacterial conjunctivitis, then there are topical antibiotic drops. If there is redness and eye pain, please see an Opthalmologist soon.