Sure! Go to Settings page, enter your email and API key from Omnisend/Mailchimp account, then select list and that's it!
If you’d like to import the emails this app collects into email services Mailchimp or Omnisend, you need to copy and past the “API Key” from those apps. It will look something like this “4525ee...04241a3”.
To get it from Mailchimp, go to Account → Extras → API Key → Create a Key. Copy/paste the created key into API key field in Settings page.
For the OmnisendAPI key, go to My Account → Integrations & API → API Keys → Create API Key (choose the option “This API key will only allow to add new subscribers”, and give it any Name). Copy/paste the created key into APIkey field in Settings page.