Yes you can put Styrofoam containers into a microwave for a few minutes to re heat food but keep an eye on the Styrofoam container because leaving the Styrofoam container in the microwave longer than a few minutes may cause the Styrofoam container to melt.
I've re heated food in a Styrofoam container many times without problems as long as I don't leave it in the microwave longer than 2 minutes.