Ajax is not an installation.
AJAX is based on internet standards, and uses a combination of:
-XMLHttpRequest object (to exchange data asynchronously with a server)
-CSS (to style the data)
-XML (often used as the format for transferring data)
AJAX applications are browser- and platform-independent!
In other words, you just need to create the object and start using the object to get your tasks done. You can find a very easy explanation here.
In essence everyday ajax is just js that sends/receives data from a server-side script e.g. php . So you need to bone up on js. You may find using jQuery an useful way into it as ajax objects in vanilla js are quite a difficult proposition