Installing windows 8 using bootcamp or virtual box I've been looking around and haven't found an idiot proof guide to partitioning my mac to run windows 8. Unfortunately, that's what I need as I have not knowledge of any of the required software/firmware or OS's in general.

I'm running OS X 10.10.3 with bootcamp v 5.1.4 and I also have virtualbox 4.3.28

I have ownership of a copy of windows 8.1 student from the microsoft store but the only thing I've been able to download there is an .exe file.

I think the problem is that I don't have a bootable usb or iso from which to boot. Is there any way for me to install windows on my machine?

Also, what would be better for uses like CAD on the windows partition: virtualbox or bootcamp. I'm running entirely on a solid state drive (MB pro) so rebooting isn't a huge issue but I wonder if it's worth it in terms of performance to use bootcamp.

Sorry for the long-winded two part question.
With just having an .exe file you'll need to run that under Windows to create either an USB Installer or an ISO Image or both as they can be used for either Boot Camp or in a VM using VMware Fusion, Parallels Desktop or VirtualBox.

To install in a VM you can use an ISO Image.

To install using Boot Camp Assistant and creating a USB Installer you need an ISO Image to create the USB Installer if the one created under Windows will not work.

If your Mac has an Optical Drive a DVD can be used, creating it from the ISO Image.