Mad_Jack
Legend
Also, if you want to have anything on the spine of your book, you'll need to look at lulu's preview of the cover and then figure out how to free-hand that onto your combined covers file (or at least, I did).
If you rotate the image 90 degrees so that the spine area is horizontal, you should be able to use the Text function of whichever program you're using to add the text to it. Once you're done, just make sure that the text is part of the background image instead of still being a separate item, and rotate your image back to its original orientation.
It's simple enough that you can do it in Paint if that's all you have.
I've never used lulu to print a book, but the basic process for making a single front-spine-back cover image is:
Open a new image in Paint or whatever you're using, and make it 11 inches high by 17 (which is 8.5 times 2) + X inches wide.
X is however thick you need the spine to be - the place you're uploading the final image to should have instructions on that. (They'll also probably tell you whether or not your image needs a border (blank or colored) around it.)
Find the largest, highest quality versions of your front and back images that you can.
(Resizing them can alter the quality if you change them too much, so making them a little smaller is always better than trying to make them bigger.)
The simplest thing to do is simply open them up in whatever you use to view images and then just right-click and copy the image.
Go to your new image, right-click and paste the back cover image into the left side of the new image, resizing it and making sure it's lined up well against the side, top, and bottom edges (zoom in for this part). Then copy the front cover image and paste it into the right side of the image, which should leave a blank space in the middle of the image however wide the spine is going to be.
Rotate your image 90 degrees so that the spine area is horizontal and use the Text function to add your book title.
If you're recreating a cover for an existing book, just find an image of the book's spine online somewhere and use the snip-and-sketch function of your browser to select the appropriate area, cut it out and copy it to your clipboard so you can paste it into the appropriate area on your new image.
Rotate your image back to its original orientation, check your work carefully, and then save it as a PDF*... Unless there's a specific limit to the file size of the PDF, save it at as high a quality as you can.
*If you're using a program that won't natively save your image to PDF format, save it as a JPEG or PNG, and use one of the free online converters.
The process may seem daunting at first because there are multiple moving parts to it, but each part in and of itself is relatively simple - it's just a bit time-consuming - and if you're bothering to print out a book, you might as well make it look good, right?