Go to https://www.klaviyo.com/ and log-in. 

Need a log in? Ask Andrius.

If you have acces to more then one country, always check if you are in the klaviyo off the right country. You can do this in the bottom left corner of the screen.

Then click on Audience in the menu at the left side and List & Segments.

Then go to Newsletter (this can also be standing an a next side.

Then click on Quick Add.

Fill out the info. Only the e-mailadres, first name and last name are needed. Also remember to put a checkmark under Email (Profile has granted explicit.....) 

And push on Add subscriber in the bottom. 

The customer is now subscribed and should soon get the welcome e-mail.