iControl is a core component of BIG-IP so there is no need to install any additional software or license additional components on the BIG-IP to start accessing the APIs.
To get started, I'd recommend you download the 4.x SDK from the iControl downloads page. In the SDK there are some java samples to get you started.
http://devcentral.f5.com/LinkClick.aspx?link=http%3a%2f%2fdevcentral.f5.com%2fdownloads%2fiControl%2fsdk%2fwindows%2fiControl-4.6.3.zip&tabid=73&mid=656
Click here
Keep in mind that the APIs have changed from 4.x to 9.x so anything you build that is directed to a 4.x platform will not work with 9.x.
If you are able to migrate to the currently supported product line of 9.x, you can make use of the iControl library for Java that I wrote that wrapps all our SOAP client proxy code (for Axis) into a single java library. We also have a Java Wrapper project in the Labs that does some "use case" wrapping of the API calls.
Good luck!
-Joe