On page three of the Hosted Store User Manual I am seeing
All emails automatically sent out by the store are editable here. You can also edit the header and footer of the confirmation thanks page and the packing slip and invoice footers and headers.The fields will accept HTML so you can format the displays how you like. There is also dynamic replacement text so you can choose to show things like the customer name, order id, order date etc depending on the type of email.
From within the admin go to Store Admin > Email Messages & you should have the ability to edit all the emails sent out by the store from there.