Stitch the main crown pieces together, exactly the same way you did the lining. If you added a pocket, it's slightly easier if the piece with the pocket is one of the middle sections of your pie-halves, but it's not a big deal.
Now, put the crown and the lining together, with all the raw edges inside. Pin around the edges and run a line of stitching to hold the lining in place to the crown. It should be starting to look like a real hat now.