There are two possible ways you can do this action with MailerLite. The first one is by sending a freebie in an automation workflow. To do this, you need to create a form and offer a free gift in exchange of joining your list; then, create an automation workflow that activates when a subscriber joins that list, and lastly, create an email containing the external link to download the freebie. The other way you can choose is by sending the freebie in the double opt-in confirmation email. Just create a form with the same characteristics, turn on the double opt-in in your form settings and create the opt-in confirmation page with the link to the gift.