This applies to the Legacy store only. If you are interested in editing the message for the new storefront, see Store Configuration\Look and Feel\Messages.
The introduction page of the store is laid out using the Description area of the Store menu. It is a simple page with the HTML editor on it that allows the user to create the page. Telling Stone will work with you to configure your initial description, but you can come here if there are minor edits you want to make to the content. This is an HTML editor and the description is HTML so things might not necessarily look the same here as they will on your storefront. You can use the "Preview" button above the editor to see what it will actually look like:
The resulting description on the storefront appears in the space outlined by the red frame: