Tracking Opt Ins from Advertisers

I’m a little new to both Klaviyo and how to track analytics.  I have an ecommerce website for a small niche and some of my advertising is banner ads on web forums or in digital magazines related to that niche. What I’d like to be able to do is track email opt-ins (not just website visits) to know exactly how many email leads are coming from each advertising source.  I have an entry pop-up (and an exit) to capture both emails and SMS on my website.  Is there a way that I can somehow set up Klaviyo to allow me to see how many email opt-ins are coming from each source?  Thanks for any suggestions!