1. If you have your own website, you can create a page that has the downloadable on it.
2. You can also use something like MailChimp, which will also collect the email addresses for you. (We use Flodesk, which we LOVE – try it our here in our affiliate link)
3. There are loads of other services available to do this, from free to premium.
If you’re not confident in creating a sign-up form on your own website, use a provider like Mailchimp to do it for you.