while I don’t want to disagree with you but obj support was added in UE4.2
from the 4.2 release notes.
@Knight526806, you should be able to import your obj and tga’s although as qdelpeche pointed out with those links fbx support is much better then obj, you might want to think about importing your obj into a 3D app like blender and then exporting to fbx.
to answer your question, import the model and the textures, create materials using your textures and then apply the materials to the material slots in the model viewer.