For generated emails, you can edit the subject line to whatever you want.
Specifically, for Promo emails, you can edit much more, such as:
1. Segment - This is where you decide who you want to receive your Promotional offer. You have three options between Everyone, Buyers, and Non-buyers.
2. Discount Type - You can select from No Discount, $ Discount, and % Discount.
3. Discount %/$ Off - Here is where you decide how much of a discount, based off type, you want to offer in this Promotional email.
4. Minimum Purchase Amount - This is the threshold your customer must purchase in $ before a discount can be applied. This discount can be any amount, ranging from $0 - $1,000,000.
5. Promotion Start/End date and time - This is the window when your Promotion will be active. Soon after your promotion start time, your Promotion email will send. As soon as your Promotion ends, the discount codes you sent out will no longer work on any purchase.
Here's where you edit all that information:
To get to that page, click the "Advanced" button when you're in your editor view of your email:
If you want to edit the specific part of the email, like image and the wording click on the little "Pencil" button at the bottom of the email:
This will open a new set of options you can edit the details of the email:
1. Header Copy - This will show in a header of the email
2. Image - You can select one of the predefined images here
3. CTA - Text on the Call To Action button
4. Text - Wording on the image
5. Callout Copy - Here you can change the discount shown in the header of the email and the text inside the image