Artisans are special workers that assist you in constructing or upgrading your City's buildings. Each additional Artisan adds an extra construction or upgrade queue to your City, allowing you to upgrade or construct multiple buildings simultaneously.
To purchase an Artisan place your cursor over the numbers above the "Construction" button, click "Purchase Artisan", view the information about the price in the pop-up window, and click "Purchase". NOTE: The number of Artisans you may purchase is limited. Once purchased, they stay in your City forever.