F9 function key to access the UEFI Boot Menu? Sounds like you might have an HP laptop. If that's the case, and your HP laptop acts like my HP Envy DV7, then you have to jump through some hoops to get Fedora to be the "default" boot OS.
First off, understand that when you install Fedora in UEFI mode alongside Windows8/8.1, Fedora makes itself the default OS to boot in the EFI System Partition, so, on most laptops installing Fedora this way with UEFI and dual booting with Windows, you get the grub2 menu at bootup.
On some (or all?) HP laptops, HP has has jiggered the UEFI boot up so that if finds any other OS other than the originally installed W8/8.1 is not the first OS in line to boot (default), it rewrites the UEFI boot menu making Windows the default. Thus, you never get the grub2 boot menu, it just boots straight to Windows.
You need to learn to use the efibootmgr tool (command line) to help you see what is going on. Just run
efibootmgr command without any arguments, as root. Here's what it looks like on my HP laptop.
Code:
$ sudo efibootmgr
BootNext: 3006
BootCurrent: 0006
Timeout: 0 seconds
BootOrder: 3000,3006,2001,2002,2003
Boot0000* Windows Boot Manager
Boot0006* Fedora
Boot2001* USB Drive (UEFI)
Boot2002* Internal CD/DVD ROM Drive (UEFI)
Boot3000* Internal Hard Disk or Solid State Disk
Boot3006* Internal Hard Disk or Solid State Disk
Notice the BootOrder. Normally, one can change the boot order using the efiboomgr program. I can do that on my HP laptop. But when I boot, my changes are undone and Windows is made the default again. "3000" corresponds to the "Boot0000* Windows Boot Manager" entry, which boots W8 and "3006" corresponds to "Boot0006* Fedora".
My workaround is to set the "BootNext:" to boot Fedora with efibootmgr. Fortunately, HP's tinkering doesn't mess with that setting, so now when I turn on my laptop, it boots straight to the Fedora grub2 menu. The caveat of that is, no matter what I've tried, I cannot get grubs Window entry to actually boot W8 on this laptop, so to boot into Windows, I resort to hitting the F9 key for the UEFI Boot Menu and boot Windows from there. After booting into Windows, the BootNext entry is cleared, so getting back into Fedora then requires the F9 key again.
Since the BootNext entry is a "one shot" deal, to keep it alive for the next boot, I put an entry into my rc.local file that runs at bootup on Fedora to re-issue the boot next command so Fedora will once again boot on the next boot without my intervention at the keyboard.
Code:
$ grep efibootmgr /etc/rc.d/rc.local
efibootmgr -q -n 3006
This may or may not be your situation, but if it is, the info I've just outlined should help you.