Once the Winamp media player software has been installed on your Windows PC, you can download the AjaxAMP Remote Control Plugin for Winamp. Unfortunately AjaxAMP is no longer developed or supported by the author, but the latest version is still available here: AjaxAMPInstallerv3.3.zip
Alternative sites:
Winamp Enthusiasts on Facebook
If you already have it installed please ensure that it's version 3.3 as it contains some important bug fixes.
Once installed, it's important to configure AjaxAMP. See the next section for help.