Add more tabs in tab view controller storyboard

Add one view controller (UIViewController) And Add it with your tabBarController in relationship “View Controllers”(To do this right click on tab bar controller and drag it to new view controller and select bottom most relationship seague, i.e. view controller), your XIB page should look like: 

enter image description here

You can apply same pattern for the rest.

To Add Controller Files

You have to go to the menu and click on “New File”, then Objective-C class, and finally make sure to select UIViewController subclass. Name it and then it will add the files. Now in your storyboard make sure to change the class of each tab to the name of your file. i.e. to assign custom class for your ViewController this I have used Name AAA for that in Image.