I’ve noticed that you have asked about this issue before in another thread where you needed to put this code in the root directory, and now in this thread you need it in the backend.
This forum is dedicated to Corvid. You will need to contact the service provider for assistance in adapting it to use in a Wix site.
Since you “don’t know much programming”, you might want to consider hiring a developer. Check out the WixArena - it’s a hub where you can look for Corvid (and other) experts for hire.