To import followers, you go to Contacts => Grow Followers.
Then click on the button Get started and follow those steps to import.
Besides that, you can grow followers through different channels as following:
Collect Followers At Checkout
Create Follower Collection Page
To get its instruction in detail, please simply click on the button "Get started".
Should you need further support, please feel free to contact us via live chat or email us at email@example.com.