Where do I sell mead and trade dragonite fragment?

Mead, and other items gained from exploring are found in your items / inventory and can be sold simply be tapping on then and then on the 'Sell' button.

Dragonite fragments are used to exchange for materials in the Material Shop. This is in the Blacksmith building although you can access it by finding the fragments in your items and tapping the 'Use' button. If you go to the blacksmith, tap on the 'materials' option and then on the 'Material Shop' tab at the top.