does someone knows how to upload a custom cover and remove all the headings? Which template I should use?
Just choose any of the cover templates that allows a full-bleed (a whole page) image for the front and back covers with text boxes on top then don’t put any text in those boxes. If BookSmart has put titles, etc in for you just click in the text, select all, and delete the text. For a 10" x 8" the 5th template in the list is a good one, for the 13" x 11" the 9th or 10th.
If you do that and go into Book Preview (the button at the bottom right of the BookSmart window) you will see that no text is printed.
With the spine, if you want that blank, just showing the background colour, just delete the titles that BookSmart has put there. With the flaps just don’t add any text – from a quick look at the templates I mentioned above there are no full bleed flaps so your options for creativity there are limited.