You can make items using production buildings. The type of items that you produce depends on the building.
In order to make an item, tap on the building, scroll through the recipes on the right until you find the one you want to make. The data under the item’s name indicates how many minutes the recipe will take to complete.
On the left, it shows you what ingredients are needed to make this recipe. To start production, drag the needed ingredients from the left onto the building in the center.
The current item that is being made is in the far left slot with a timer showing how much longer it will take to complete.
You can choose different items to make by swiping the recipes upward or downward. Recipes are unlocked by level.
Production buildings can only make one recipe at a time, but additional slots allow you to have more recipes in queue and ready to be made as soon as the previous one is done.
By the way, you can use rubies three ways to make production go more quickly and efficiently:
When the item is done, it appears near the Building with a shiny effect. Tap on it to collect it. Items produced in the buildings are stored in the Barn.