How to add the newsletter icon to the side of the page - DAWN

[hodiniki]

Hello!

I have a question about how can I add this little newsletter icon to the side of the page? 

Like in this website: https://perrocollection.com/

I like this way really much, and I do not want to have any popup window. 

Is there any app what I can use for this purpose? I didn't find any. Maybe someone found a good one, I really appreciate it if someone can help me with this issue.

Thank you in advance!