Shrinking Windows 8 method
The simplest approach I've seen thus far when dual booting anything with Windows 8, has been to first use Disk Management to shrink the Windows 8 partition so that there is room on it for another installation.
Once you've shrunken it, you can use whichever distro you want to perform the installation using the space that was just freed up. Doing it this way gets you around having to monkey around with UEFI in any way.
Here's a guide titled: How to Dual Boot Windows 8 and Linux Mint on the Same PC, with the various steps in dealing with Disk Management down to the installation of Linux Mint.
Windows 8 1st, Linux 2nd
This method titled: How to dual-boot Windows 8 and Linux, is similar but if you don't want to shrink the partition, you can try this method instead. It opts to not use Grub to manage the dual boot, but chain load into Grub from Window's boot manager.
Resolving Boot Management & Grub Issues
Useful resources for getting either Window's Boot Manager to play nicely with Grub or vice versa:
If you're determined to get Grub working as your primary boot manager you can see how to address that in this post: