Overlapping UVs in Blender?

Hi,

I'm making some custom clothing for ts4 and followed a tutorial on it. When I was in blender I tried uv mapping and my mesh was overlapping with the body. The tutorial said to merge the nude top mesh with the custom mesh and the uv of my mesh is overlapping the body. (I deleted the body that is under my mesh to lower the poly count but that didn't help with the uv) 



I'm used marvelous designer to mesh the shirt if that makes a difference.

I'm also using a mac.

Thanks!