If you use ActionSprout to campaign on social media, you can integrate with Action Network to subscribe those activists to your Action Network email list through Zapier.
To set up the integration, follow instructions from ActionSprout here. You'll need your Action Network API key, but all of the set up for the integration is done in your ActionSprout and Zapier accounts.
Integrating with ActionSprout is a feature only available to paying partners. To become a partner, please visit actionnetwork.org/partnerships