This is from a CF6-50 engine. Other engines have different location of the accessory gearbox.
In the picture above you can see the location of the starter in relation to the fan.
Above is a picture of the starter. Bleed air enters at the front and is expelled out through the mesh into the nacelle. It is eventually discharged overboard through vents in the cowling.
Above is a picture of how the starter is connected to the HP spool via the accessory gearbox, transfer gearbox and tower-shaft.