Help with assigning materials to meshes

So I imported a texture and then assigned it to a material. But whenever I try to drag the material onto the object that I want to have that material, instead of taking on the detailed material the object just turns a solid color that looks like the average color of the material.

Any one know why this is happening? If you need me to elaborate I can.

Like dsada said, it’s probably the UV’s. Open your model in your 3D modelling program and make sure your mesh is unwrapped.