How to set a button on an email to put a tag on a contact

Hi,

My first post here on the community forum.  

I’m wanting to understand what I need to do to structure a button on a Klaviyo email put the contact clicking on the button onto a new list.

What I’m trying to do is make it on an email where a contact can click on the button if they want to receive another flow that contains a certain educational sequence that we offer.

However, I don’t see where I can configure the button (on the flow email editor) to either place a tag (which I could use to initiate the new flow) or put the contact on the list for the other flow.

A developer told me it was possible by having a custom property be added to the url of the link that the button clicks to.

Any ideas how I might structure this?

Thanks!

Will