Go to the menu Windows-> Rendering Editors-> Hypershade
From the menu on the left, select a surface. In your case, something simple like a blinn or a lambert. A sphere will be created on the right of the Hypershade menu. Double click it to edit its options like color and reflectivity. then 'Middle Mouse Button drag' it to the object in your camera view that you want it to go to or select the object first then right click the texture and choose 'Assign to selection'.
And after calming me down with some orange slices and some fetal spooning,
E.T. revealed to me his singular purpose.
--TOOL, 10,000 Days---