Hey @Philip Stine34! I might be a little confused by your question. How are you ultimately wanting to deliver the freebie to those existing subscribers? And how would you like for them to indicate to you that they're interested in receiving it?
If you want to deliver the freebies via incentive email38, then the subscriber would have to sign up to its respective form or landing page to receive it. That said, it's very normal for the same subscriber to sign up to multiple of your forms/landing pages for different freebies! And since we're a subscriber-centric provider32, they won't be duplicated on your list, we'll just add it to their existing profile. This is a great way to start building up profiles of what your subscribers are interested in!
Alternatively, if you don't want them to have to opt-in to a form to receive it, you could just add the freebie to one of your emails and send it to your existing subscribers that way (instructions on that included in this guide48). Or you could set it up in a sequence that's triggered by a link trigger43, and send out an email including that link, with the CTA being to 'Click here to receive XYZ' (or what have you). Then if they click the link trigger, it'll trigger the sequence to deliver it to them.
(In case you're referring to disabling double opt-in30 for existing subscribers, then that isn't possible — double opt-in is on a per-form/landing page basis; it can't be turned off for existing subscribers. You can, however, modify the incentive email so that it's more specific to what they just opted in for as opposed to the default/generic 'confirm your subscription' language.)
Please let me know if I may have misunderstood something about your question, though! ☺️