The starter in a 1990 Toyota Camry is located on the
bottom of the engine, towards the passenger side (right side in the US). You'll likely need to get underneath the car to see it clearly. It's usually attached to the engine block near the bell housing (the area where the transmission connects to the engine). It will be a fairly large, cylindrical component with several thick wires connected to it.
Because accessing it often requires working under the car, be sure to use jack stands and follow safe car lifting procedures. Never work under a car supported only by a jack.
