I am installing an AdRoll pixel on all pages of my Wix site and I need to learn how to apply it to all individual product pages.
I do suggest that you look at AdRoll Pixel own support pages before coming here and asking.
https://help.adroll.com/hc/en-us/articles/215505827-Wix
Or you can do it this way.
https://help.adroll.com/hc/en-us/articles/212675687-Google-Tag-Manager
For which Wix Support already have their own pages about using it here.
https://support.wix.com/en/marketing-tools-analytics/marketing-integrations-tracking