Hi,
1. Go to the search instance options first, under the Ajax Search Pro submenu: https://i.imgur.com/UKONDZX.png
2. Then navigate to the Advanced Options panel: https://i.imgur.com/wYHxfGL.png
If you don’t yet have created a search instance, make sure to read this chapter of the documentation: Getting Started
You will find many valuable information within the documenation.