All your past customers who made a purchase from you are automatically added to Soundest as subscribers. Also, new subscribers, who sign up for newsletters via Soundest signup forms on your website are added to your contact list. If you use any other signup form tool, use API key to connect it with Soundest.
Data from your online is synchronized once a day, so it means that your contacts list are updated on a daily basis.
One more thing: Tictail users who use Follow Plus app for collecting contacts do not have to do a thing - gathered contacts are automatically added to Soundest. No manual import is required.