How to activate the Circle to Search feature on Pixel phones?

I can't seem to find out how to start to use the "Circle to Search" functionality on my phone (Google Pixel 8) as explained in https://support.google.com/android/answer/14508957 . It mentions the '3-button navigation mode' but my phone doesn't have a bad with three buttons like that. Mine is a bar with Google icon on the far left, and three buttons on the right: a magnification glass for AI search, a microphone for audio input and search, and a camera icon for search with camera. So how do I start to use the 'Circle to Search' function?