Depending upon your environment, you will need to learn how to configure Jaxcent for the type of server you have.
The Jaxcent download package includes documentation on getting started, as well as the Jaxcent API.
In addition to the API and environment, AJAX programmers using Jaxcent should focus on learning the various types of HTML tags and styles. HTML styles are often called "CSS" (Cascading Style Sheets) by HTML programmers, because historically, many HTML styles and separate style sheets were introduced together. However, for an AJAX programmer, an HTML style is an HTML style, whether it comes from a CSS or not. Some HTML tutorials are:
Jaxcent can be downloaded from http://www.jaxcent.com/