Select your Alliance icon, which is symbolized by a shield and two swords an the top left hand corner next to your Profile image.

Selecting this icon will take you to the Alliance profile.

When you first start playing Dawn of Titans, you are asked if you would like to join an Alliance or to create your own Alliance.

Selecting the Search icon along the bottom of the screen will allow you to search hundreds of Alliances where you can view their details and then decide to join one of them.