If you haven't already, you can obtain a copy of the latest version of the API using one of the links on the Downloads page.
Installing 51Degrees Java API is as simple as adding the reference to the JAR file to your project or specifying the API as a maven dependency. As of version 3.2 of the API the Lite data file is no longer embedded into the JAR file, therefore you will need a data file. Premium and Enterprise data files can be downloaded manually or using the auto update capability built into the API. The latest Lite (free) data files can be found in the "data" folder of our git repositories or if you don't want to clone an entire repository, download the data file individually from github by clicking the "raw" button.
Once you've added the JAR file to your project you are ready to go.