Help with adding different textures to my object?

Hey everyone,

I am making a level that is supposed to be a futuristic city/army base. I am now design my own textures for each of objects. I would like to know how to add one texture to a certain place on my square object with applying it to the whole thing as posted in the picture below. So I would like to leave the yellow color on the largest square. And then I would like to add different textures to the buttons. (first image in the link)

One other note: In relation to this question, I made this object in Maya 2020 and I have attempted to hand model the object because I thought there might be a mesh issue. I was wondering how I could convert my blue print to a teal FBX so that I can edit it in the model viewer? (second image in the link)