To integrate your MailerLite account with BookFunnel, go to your top right dropdown menu and choose integrations. Choose BookFunnel and copy your account API key.
Now log in to your BookFunnel account. From the left-hand menu click integrations and choose MailerLite. Next, just paste your MaiLerLite API key here and click enable MailerLite integration.
To see if the integration is working, add a new page. Select a book and make an new giveaway page by clicking "Yes, collect the readers email adreses". You will be able to choose the group to sync with from your MailerLite account. There you go, thats how you can use your BookFunnel integration with MailerLite.