Upload the ajaxsearch.ocmod.zip file from Extensions > Installer. Refresh the Modifications from Extensions > Modifications. Then Go to Extensions > Modules.You will see the Ajax Search module.Click on Intall. After successful install You can configure the settings as per your requirements.

Extract the zip file.open the 2.3x/2.x folder.Upload admin,catalog folder to your server from the "Upload" folder.
Upload the install.ocmod.xml file from Extension Installer. Refresh the Modifications from Extensions > Modifications. Then Go to Extensions > Modules.You will see the Ajax Search module.Click on Intall. After successful install You can configure the settings as per your requirements.

Enable the module status and Add Language variables. Select Search in Product fields,choose product fields to display. Enable/Disable Category Search.Select Search in Category fields,choose category fields to display. Enable/Disable Manufacturer Search.Choose Manufacturer fields to display.