Need help locating a file

When you go to my website:

https://amberandsteph.com/

and enter name and email a message pops up saying “So thrilled you’ve joined us”. I want to alter this text but for the life of me cannot find the file to edit.

Can someone help me locate this file or perhaps point me in the right direction. I’ve searched the chimpy lite plugin files to no avail. Firebug lets me edit it but obviously it doesn’t stay permanently and it only shows me where the css is located. I need the fild where html is located.

Thanks!

P.S. If you put your name and email in to see the message I will delete you from our list so you don’t get unwanted emails from us. ??