Hello @ChristineS755 ,
Here's guidance from our Inline/Pop-up Installation article:
Widgets can vary depending on your chosen theme. If you don't see a widget for your footer, try looking for the footer settings for your chosen theme by clicking Appearance > Customize and then clicking Footer (if available) to edit the footer content. Sometimes the theme has its own named tab in the Dashboard Menu, and you can edit the footer from there. If you don't see any of these options, you have to edit the footer code by clicking Appearance > Editor > footer.php. Please note that if you later change the theme, the sign-up form code is stripped out of the footer.php and you have to add it back in again.
For help adding the code to your Wordpress.org website, please contact your webmaster or view Wordpress.org's support.