Joining model

Hi, i just got blender today and i never done any 3D things before.
I followed this tutorial. Bellorum’s Corner - Headmodeling tutorial
In the tutorial it had me delete one side of the model, then duplicate and mirror it.

My problem is, i don’t know how to join the 2 sides. I tried clicking the vertices and merging them but the model still seems whacked in texture view.
Link to my Blend File