Do not start with two projects, as you'll have an incredibly difficult time integrating them into one app. This is pretty simple, but you do need to learn the basics of view controllers.
Use Storyboards, and start with a single view app, maybe inside a navigation controller. Then do a transition to a tabbed view controller.
Upgrade to Xcode 4.6.3 or 5. Look at Apple's template apps for a tabbed application and a single view app to see how the storyboards look. Then copy the storyboards in one to the other, and link them up. This is definitely possible and straightforward, but you do need to understand how each view controller works with the others.