I read its nice library.
But I don't understand why it is so complicated to install it.
Is there simple way to just download, and link the libraries ?
I suggest playing with the sample apps and reading some of the three20's manual before you add three20 to your project. That's how you can get a feeling of what the framework can do.
After that, create a new project and follow http://three20.info/article/2010-10-06-Adding-Three20-To-Your-Project