Power Store does not have the ability to create a Master options set, the options must be entered for each item individually.
The Sell Something here section of the main page can be edited using the content management feature of the admin section. In the content list select the home Page, then edit the header or the contents
Also using the content management , you can edit the store message section, using the flash icon, you can add a flash element to the store message section to display your flash under the menu.
