Update existing contacts from WHMCS

Hello, i am trying to integrate mautic to whmcs, the idea is that when a user register contact being created automatically in mautic, and existing contacts should be updated too (this second is not so important)

I have this script in my whmcs footer… what else do i need?

I am not 100% clear on what you are trying to achieve, however there are two ways to pass data to Mautic, one is through the tracking script with the mt send (you must make sure to have the fields you are sending publicly updatable) and the second way is via API. Api can be integrated with either code, or using something like zapier or we use n8n self hosted.