If this is for a list of existing leads from your DB you want to invite to the event, then in your email you could just have a link. The text in your email to say just click here to RSVP. Then they are taken to a thank you page. In your program, you're listening to that click from you're existing lead to update a status and send out the confirmation email.
If this is to promote on your website then you will need a LP with a form to capture their details (could just be an email address) then again, your smart campaign listens to this form to trigger the confirmation email.
You would set up a campaign for this and use the "Clicks Link in Email" trigger and select the appropriate email and the correct link for it to be listening for. That would be your Smart List.
Your flow would be whatever you want to have happen if they click on that email. Maybe "Change Program Status" or "Send Email" or "Create Interesting Moment" or whatever is appropriate.
If you just wanted to run a report to see all the specific leads who clicked on that link, you could set up a Smart List and use the filter "Clicked Link in Email" and agains select the email and the link. This will produce a list of leads who clicked, which can be exported from Marketo if need be.