If you'd like to change a products attribute in the Magento Admin, simply find the product you would like to change by navigating to Catalog->Manage Products. Once you have found the product that you would like to modify, click "Edit".
Next, find the attribute that you would like to modify. In this case, it is labeled as "Coming Soon Product".
Change the attribute to the new value. In this case, we want it to say "Yes" for all the new Coming Soon products.
Finally, click Save and Continue Edit.
It's strongly recommended that after making changes to the products, you re-index your store so that all of the changes are sure to take effect immediately.
To do that, click System on the navigation bar, then click on "Index Management". In the upper left of this page, click "Select all", in the upper right make sure the Action is set to Reindex Data. Then click submit.
Your changes should now be visible.