Unfortunately, getting Linux to boot on a Mac can be tricky. Macs use EFI, which is weird, but Macs use their own variety of EFI, which is weirder. It can
be done, though. Broadly speaking, you have two choices:
- Google around or wait for somebody to reply with instructions and try them. Stare at a blank screen if it doesn't work. Repeat until you stumble across an approach that does work. Don't ever modify the way the computer boots, lest you end up unable to get it to boot again.
- Learn enough about EFI, CSM (EFI's BIOS compatibility layer), and various boot loaders to create a working configuration in spite of whatever your distribution has set up. You'll then be able to get it to work in the future, too, if/when you modify the setup.
The second approach will probably
take longer in the short term, but it'll serve you better in the long term. Unfortunately, Web resources are few and far between. Many Linux-on-Mac tutorials simply provide a "recipe" to get it to work, often involving BIOS compatibility, without providing much in the way of background information.
If you care for some background information, my Managing EFI Boot Loaders for Linux
page provides information on EFI boot loaders; however, it's not very Mac-specific. I've got my own Linux-on-Mac tutorial,
but it's geared toward Ubuntu, so many of the details will differ for a Fedora installation. Still, between the two, that should help you understand what's going on and how to get it to work for you.