You have to take your mesh back into your design program be it Maya or Blender, etc. and assign different materials to the mesh areas you want different Textures added to. You have to do the work, no way around it. It is all part of developing. While the Unreal Engine does a lot of wonderous things and you can create simple models in it… It is not a tool like blender, or others out there. I personally use one of the others. Once you have assigned the material layers that you want your textures to go to bring it back into Unreal and there you can then work your magic. Unreal is wonderful and I currently use Unreal Engine 5.0…can’t say enough about it.