To create and schedule a new sales event for your Etsy shop click the + New Sales Event link on the Sales Event page.
Enter the specifics for your sale and click the Schedule Sales Event button.
You can choose to run a sale for all listings in your shop or just a specific section.
You can also write the "on sale phrase" that you want prepended to either the title or description of every item on sale.
If you select the Auto-Add option, items you add to the sale section of your shop while the sale is running will be automatically discovered and added with the sale prefix and discount applied.
This allows you to add new items to your shop while the sale is running and Etsy On Sale will take care of discounting them and changing them back at the end of the sale.
Auto-add searches your shop for new items 4 times a day. If you want to have new items found immediately you can use the refresh sale button.
If you select this option, the original price for each item will be displayed crossed out on the Etsy listing page like the example below. This gives customers an easy way to see the size of discount you are offering.