Hi there @MollySpace48,

Welcome to the Community and thanks for posting your question here! Glad to hear you’ve so far smoothly migrated over from Mailchimp and are looking to add contact form 7 features in your Klaviyo account.

As a note, Contact Form 7 does not have a direct Klaviyo integration at this time, but you may be able to connect via our API. You'll specifically want to use List API V2 in this doc: Klaviyo's REST API References.  Alternatively, you can replace the form with one of Klaviyo's. Take a look at our form instructions in these linked guides: Create a Signup Form from the Form Library and Guide to Creating a Signup Form.

So to me it sounds like you are looking to tag profiles that enter your database with a property that defines a source for what content they downloaded? You are right in the case that these people would be grouped into lists within Klaviyo based on the profile properties or tags you associate with them - but that is up to you on how to organize each person. If the form you have made is from Contact Form 7, which would be a third party form,  you can set up the redirect to be adding and sending users to your designated Klaviyo list. 
You can find instructions on how to create this redirect from the How to Redirect Existing Signup Forms to Klaviyo article. 
I would also double check to make sure you have confirmed your subscription as well per the Guide to The Double Opt-In Process if your list still has double opt-in enabled. With double opt-in enabled, if someone signs up to the form, but do not confirm their subscription, the contact would not be added to the respective list. Only by opting in and confirming their subscription would the contact be added to the list. 

There is also a community guide that goes over how to use the $source tag instead to group contacts!

I have found this article from wordpress that may be of use regarding contact form 7 and Klaviyo which could be worth checking out.

Hope this helped!
Alex