Alt+M to merge verticies. Just select one vertex on the shoulder, and one vertex on the long rod, then just merge them together.
Alternatively…if you go into edge selct mode [ looks like a \ instead of the triangle for face slelect mode] and right click the edge, (shift)right click the next edge. Then push ‘F’, and you’ve got a face. Repeat for other faces, and you’ve got a neat join