This tutorial describes how to enable the MailChimp auto subscription feature. So, when a user subscribes to your website, they will be automatically added to the subscription list on MailChimp.
Set the firebase config variables for Mailchimp configuration (you can find API data on your account)
{
"config": {
"mailchimp": {
"dc": "<DATA_CENTER_FOR_YOUR_ACCOUNT>",
"listid": "<LIST_ID_YOU_WANT_SUBSCRIBE_TO>",
"apikey": "<LIST_ID_YOU_WANT_SUBSCRIBE_TO>"
}
}
}