Oh, it's an admin privilege so I'll just make you an admin. When your putting the update notice (which is an image, right?) you need to go to the search box and type Template:Main Page/Slider and switch the image with the Galaxy Standard image. Add any other information, and a link. Once you save it, the template will automatically save to the Main Page template and show up on the home page. If you need any help editing ask me.
Check out your Admin Dashboard, which can by found by clicking "Admin" on the bottom toolbar -- it has links to all your new tools. Please let me know if you have any questions, and good luck with your new (old) wikia!