Hm, you just added it in? If it's a part of the skin (I'm assuming that's what it is, and not a shoulder pad :P), then you're gonna need to merge the vertices. Select the verts you want to merge, then Mesh>Merge. You might need to open the channel box and increase the Threshold (1 usually works) if you're merging lots at once.
Then you just need to soften those edges