Use the items marked with a lightning icon (Generators) to add new items to the board, and keep merging items until you get the one you need.
If the required item for a quest is already present on the board, it will be highlighted with a green background.

Just like regular items, two identical Generators can be merged to create a higher-level Generator.

To add a new item to the board, simply select the Generator you want and tap it again.
Note that you can’t choose which exact item will appear — a random item from the Generator’s pool will spawn in an empty cell on the board.

To check what a Generator can produce, tap it, then tap the icon at the bottom left of the board. A window will appear showing the Generator’s level and the list of possible items it can create.

Besides Generators, you can also get new items as level-up rewards or purchase them for Banknotes.