Hi Saman,
I moved your question to a new topic since it was not related to the topic where it was posted.
There are two different SDK’s available here on the Developer Zone: The EyeX SDK and the Gaze SDK. What you have is the Gaze SDK, which is a low level SDK.
Please, refer to the Developer’s Guide included in the Gaze SDK download and the documentation of the header files.
I’m guessing you found C++ Developer’s Guide for the EyeX SDK here on the documentation page. The EyeX SDK is not available for Ubuntu, it is only available for Windows (7 or later).