Changing the material only of one surface of a solid

Hi, I’m new to this software, and I’d like to know how to change the material only of one surface of a solid. Is this possible? Every time I change the material of a solid it changes each of its six surfaces.
Thank you!

Maybe try applying a material in original program to the face and different for rest. Haven’t had a need… I’d think that would work. Dont think you can strictly in TM