As I remember it was fairly easy to do. Two screws into thru bottom of dash with the ashtray out of the bracket and one into the rear bracket to fix it in place. Rear bracket is adjustable up and down. Then just put the ashtray back into the bracket.
Forgot to ask another question since you have parts. I'm also looking for a 67 interior door panel (passenger side) parchment color. Sounds like you have a 66 and I'm not sure they are the same.