Hello Antoine,
You can add the code to your website using HTML widget - place the widget on the page and insert your AdWords code into it. Please be advised, doesn't allow to load their code without fully reloading the page, while our system does not fully reload pages while navigating.
As workaround you can try to place your HTML widget with code on the website level (set holder for it "On The Entire Website for example), it should force it to collect information from whole website.
Best regards,
Eric Curtis