Is there any support for custom PHP code to add new subscribers?

Hi! I’m trying to write custom PHP code for adding new users/subscribers, but I cannot find any support for it. I have found code for older Mailpoet version, but that’s not compatible with Mailpoet 3. Can anyone help?

I need the following:
Code for adding e-mail to database.
Code for sending confirmation e-mail to this e-mail address.

Thanks!