How to Make a Better Environment?

I am new to Unity. I am trying to make an FPS, but I don’t understand some things. Is it possible to color and texture objects like a cube or sphere? I can’t even make a house that isn’t pure gray. And do I need to use another place for models? I can’t make them by using a bunch of cubes and spheres, then just grouping them somehow and resizing them?

You create materials which are a collection of textures and effects.

Right click on the inspector and click create material.

Diffuse is the simplest material which is just a single texture.

Go ahead and select your texture.

Then drag and drop the material onto the object of interest and it should then be textured by that image.