All you need to do is to include the static TypoScript file in your template.
Newsletter2go Auth Key:
Your unique auth key which can be found in your profile settings on newsletter2go.de.
The email address of your Newsletter2go account.
The password of your Newsletter2go account.
The page the extension will redirect to if a recipient was successfully added.
The page the extension will redirect to if a recipient was not successfully added.
Every field you use on Newsletter2go has a specific name. Insert all names in a comma separated list (e.g. value1,value2,value3). Make sure that the names on your list are in the same order as the form fields. Note that the field names are case sensitive. When using predefined fields like first name, last name, or email these names have to be used: first_name, last_name, email. See the API documentation for more information.
Double opt-in ID (optional):
Newsletter2go is capable of sending a double opt-in email when a new recipient subscribes. Once the customer confirms the addition to the newsletter they will be added. You have to set up a form on newsletter2go.de which uses the double opt-in service. Once you have done that just copy the id of said form and paste it into this field. If you can’t see the id on newsletter2go.de make sure ‘Developer Mode’ is activated.
This feature is optional. If you leave this empty the recipients will be added without having to confirm it.
Note that this finisher should be executed last because it uses Form’s redirect finisher.