Choose the microwave method.

Ensure that the plate is microwave-safe and after placing the noodles on the plate, cover them with plastic wrap. Leave a small space open in the plate to allow the steam to escape. 

Pour the extra sauce on top of the pasta to prevent it from drying out.

Put the plate of spaghetti in the microwave and heat it for a minute or two. Keep checking the pasta during this time to ensure it has adequately heated through to avoid overcooking it. Heat the pasta in a 15-second interval if you think it has not heated properly.