89 Ford probe check engine light reset, code reading.?

how do you read codes fr the check engine light on 89 FordProbe GT i dont have any computer scanner and nothin glike this. the car works perfectly i dunno why that light light s up every now and then. How do i read the codes? how do i reset it? instructions DIY? photos plese send to ominimicu@yahoo.com. or a link thanks brothers