How to capture URL variables as a hidden field and associate that with the contact when they fill in an Activecampaign opt-in form that is embedded on a website?

I have an affiliate ID that may be in an URL parameter and if it is there I would like to capture it. My client uses ThriveCart and ThriveCart will pass through a URL parameter of ?affiliate=xxx. The xxx is replaced by the referring affiliate ID. It was mentioned the key to having this work is to set up the Hidden fields with the exact Personalization tag for the "affiliate" field. Would this need custom code to grab whatever values are in the URL and pass them into the form's hidden field? And is that easily done, I"m no good with coding? Thanks for any insight!!