This is almost exactly the same as creating a UINavivationController.
First create a normal view controller in your story board, in the left hand pane, click on the icon that represents the view controller, and in the menu bar, under Editor, choose Embed in and choose Tab Bar Controller.
You'll now have a new tab bar controller in your storyboard, with a relationship view controllers to your existing view controller.
Create another normal view controller, and from the tab bar controller control drag to this new one, and create a view controller relationship segue.
In each view controller there'll now be a UITabBarItem which allows you to give your tab a title, icon and badge.