You can assign any View Controller type as a Tab to a Tab Bar Controller on a Storyboard in Xcode by performing the following steps:
- Drag a Tab View Controller to the Storyboard
- Drag a View Controller or for example a Tab Bar Controller to the Storyboard
- Place the mouse upon the middle of the Tab Bar Controller
- Keep the CTRL button pressed on your keyboard.
- Move your mouse (with the pressed CTRL button) and the left button pressed to the middle of the View Controller you just added
- Release the CTRL button and the mouse button
- Now a pop up appears
- Select the segue: Relationship Segue > View Controllers
- Repeat step 2 to 8 to add more tabs.