Happy to see you’ve decided to join us! Welcome @josephine1 
We don’t have a direct Mailerlite integration in our Forms apps, you can vote for this feature in our Wishlist - Mailerlite integration.
However, there is a workaround. You can use Zapier integration where 5000+ services are available (including Mailerlite).
Here is an article explaining how to integrate your Form widget with Zapier - How to integrate your Form widget with Zapier - Elfsight Help Center.
If you have any further questions, just let me know. I’ll be happy to help 