Here is rpy2.
I'd install using 'easy_install rpy2'.
Please explain me "step by step".
Thank.
Only content in the application folder will be uploaded.
So you need to just take the relevant folder and put it in your app engine project folder. Just like you would import your own modules. It will then be availble to your app engine app.
So install the thing you want to install, take it's install directory and copy it into your app engine applications directory. This is generic, it's not specific to the package you have linked to.
This is a similar question: How do I manage third-party Python libraries with Google App Engine? (virtualenv? pip?)
Note that if it's not pure python (i.e. has C components) it won't work on app engine.
GAE note:
You can use any pure Python third party libraries in your Google App Engine application. In order to use a third party library, simply include the files in your application's directory, and they will be uploaded with your application when you deploy it to our system. You can import the files as you would any other Python files with your application.
https://developers.google.com/appengine/kb/commontasks#thirdparty