To drag items into Merlin's cauldron, first tap on Merlin and cast the "Conjuring Cauldron" spell. Drag concessions or decorations from the menu on the right into the cauldron one by one. You can use the up arrow in the bottom-right corner to increase the number of items added at a time. Once you've added all of the items you want to the cauldron, tap the green “GO” icon in the bottom left. You can review the items that will be converted before completing the conversion into Elixirs.