Steps to Flash Pixel Experience Android 13 For The First Time:-
1. Download the Rom and Zignas TWRP Recovery from http://github.com/zignas/twrp_device_xiaomi_tissot_treble/releases/tag/2.5
2. Now Boot into the Zignas TWRP Recovery
3. After Booting into the recovery go to advanced and tap on tissot manager and enable Treble
3. Now clean flash the rom & format data.
4. Reboot & Enjoy
If you are already using pixel Experience 13 just OTA update or sideload the update via adb
P.S: Enabling Treble is one time process to be done if you are switching from some other custom rom to pixel experience. If you already have treble just flash the rom & format data. If you are on pe13 treble enabled just flash normally like other roms