Install the copper L-shaped contacts in the opposite manner from which you removed them. Basically, you should replace one contact on each side of the starter and then use an insulator, washer and bolt to attach.
Now put the cleaned plunger back into the cylinder. Don’t forget the spring, which must be installed first. Basically, the plunger pushes against the spring to cause resistance. Replace the cover, using the 3 bolts to secure it.
Next clean the armature with fine sandpaper or a brush. It is a long cylinder piece that fits in the field frame. It may have a long rod coming from one end.
Look for the brush holders, which should be easy to spot. They do not look like brushes, but rather like a block of carbon or other material. You should remove the brushes (some cars have 2 while others have 4) from the holder. Use a screwdriver to release the spring clips.
Now check to see if the brushes are long enough to connect to the armature. They should me a minimum of 10 mm. You should use fine sandpaper or a wire brush to clean any grime from the brushes.
After that, insert the armature into the field frame with the small coil facing the brushes. You may need to apply some fresh grease to the bearing surface, so that the armature turns freely.
Now place field frame cap over the brush holder and replace the 2 screws you removed earlier. After that, turn the whole field frame assembly over and apply fresh grease to the bearing on that side of the armature. Install the field frame back into the starter housing.
Now connect terminal to the field house if you had to separate the 2 pieces and tighten any bolts. Place the starter back into the car.