Question: I want to add version number and build number to my app in Titanium Studio. How to I can add these two to my apps?

Answer: 
I too was struggling with this. Especially after testflightapp merged with iTunesConnect. The latter needs a strict build number system. 
There's a nifty solution.

Let's say your app version is 1.2.3 You will set this in tiapp.xml. Now if you add another number to the end like so 1.2.3.1 then the first three will be used as a version number and the whole 4 numbers will be used as a build number. When you upload next build you just set it to 1.2.3.2 and it'll be a new build.
The version number of your app is set in the project's `tiapp.xml` file. A build number is usually automatically appended when you build/run the project for iOS.

You can look at the build number by opening the Xcode project file in the project's `build` directory and going to the build settings.