If you don't know what a shortcode is in WordPress, here is an article which explains it: https://www.wpbeginner.com/glossary/shortcodes/
As you can see you have 3 different parts on the edition page:
Name: The name of your formulaire
Enable: If your formulaire is active or not
Shortcode: The shortcode you need to copy/past to your page/post
The preview is where you can see what your form will look like on your website. It will update each time you make a modification!
Automatically subscribe to: These lists will not be displayed in the form but the user will be subscribe to
Displayed lists: Lists displayed with check box for users to check or uncheck
Lists checked by default: Lists checked by default on the subscription form
Display the lists: If you want to display the list after or before the fields
Fields to display: Select all the field you want to display in the form
Display the field label: If you want to display the label of the field inside or outside of it
If you select articles / post / pages here, a required checkbox will be added on the form. The text will adapt to selected articles and display a link to the articles.
Terms and conditions: Select the article to use as terms and conditions
In this part of menu you can change the style of you subscription form.