The Email Details step is the second step of creating an email. On the Email Details step you choose who the email comes from, write the subject line and preview text, and choose conversion tags.
The fields on the Email Details step
To: who will receive the email and how many people. You can't change To here: it comes from the screen and selection you started from.
From: the email address and sender name customers see. The list shows your main From Email Address and any verified additional From email addresses for this type of email.
Subject Line: required, up to 150 characters.
Preview Text: optional, up to 200 characters. Most inboxes show the preview text after the subject line. The preview text isn't shown in the email itself.
Select conversion tags (under Campaign Settings): order tags added to orders that come from this email. See What are conversion tags on an email?
How to fill in the Email Details step
Check To shows the right people and number.
Choose the From address.
Enter the Subject Line.
Enter the Preview Text.
Optional: choose or create conversion tags.
Click Continue to design the email.
Tips for subject lines and preview text
Keep the subject line short enough to read on a phone, roughly 40 to 50 characters, with the most important words first.
Use the preview text to add a second reason to open the email, rather than repeating the subject line.
Avoid writing the subject line in capitals or with lots of exclamation marks, because those can send emails to spam.
Troubleshooting
The address I want isn't in the From list. The address must be verified, and additional addresses must have the right type ticked (Customer Newsletter or Club Newsletter). See How to add extra From email addresses for newsletters.
The From list only shows WithWine. You haven't set a From Email Address. See How to send WithWine emails from your own email address.