To be precise, if you right-click on the project wizard itself, you can modify what the wizard does; but if you want to modify the file itself, AFAICT that can't be done through the IDE, you'll have to edit the template file by hand. Luckily that's not difficult, though you may have to edit the file in administrator mode if you're on Windows. I don't know whether they're write-protected on Linux or other systems as well, but you'll know how to override that if necessary.
The file in question (if you've chosen the same wizard I did; if not, it's easily findable from there) is <codeblocks home>/share/CodeBlocks/templates/wizard/console/cpp/main.cpp.
If there's a way to edit it from the IDE, I'd like to know; but if not, you can at least do it by hand.
