Applying textures to meshes

Hi there,

I have a digital surface model (.obj) and associated texture (.jpg) which I'm trying to import into Unity3D (v.5.3). I've managed to import the object file easily enough however I'm struggling with getting the texture imported properly.

From other posts, I've tried to import the texture .jpg as a new asset (success!) but in the projects panel I'm unable to drag this onto a material (sphere) and therefore drag this into the scene and use with my mesh!

Both dsm and texture are large files (the dsm had to be broken into over 40 pieces by Unity3D to load)...could this be the problem why I can't attach .jpg to material?

Please send help.

All the best, Paul