How does I put a textures on a Model

A while ago, someone game me a model to use with my Minecraft mod I am making. However, now I need that mod in an earlier version that doesn’t take the model format he originally gave me, but will still be able to take in OBJ models.

The problem is that proprietary modeling program he used can’t export OBJ models correctly, but can for X3D. However when exporting to X3D, the textures for the model are lost. How exactly do I put these textures back in, I do have the original image files (png format) where the textures were made from.

PS: if it help, this is what my Blender Screen looks like.

Add a material and add the texture to that material. Search youtube for material/texturing tutorials.

How is the texture mapped ? If by UVs do your models have UVs ?
Do you want individual objects as you have ?
What does the texture look like ?
Dos they use the sam material/texture ?

Your question is so generic (how to add a texture) but the info supplied is insufficient to give a specific answer.
Please supply a .blend file and texture for review.