Q: Will this reformat my drive a erase my current system or other installed programs and files?

Boot Camp creates a separate partition so you can install your copy of Windows 7, 8, or 8.1. It will decrease the size of your Macintosh HD by whatever size you create the Boot Camp partition at (GB)

1. Create a DVD from you ISO - Disk Utility (Yosemite): Burn a disk image to a CD or DVD. Create an ISO from a DVD - Create an ISO image for Boot Camp from a Windows installation DVD - Apple Support .

2. Install Windows - How to install Windows using Boot Camp - Apple Support

3. The following links should be helpful...

     Boot Camp 5.1: Frequently asked questions - Apple Support

      https://help.apple.com/bootcamp/mac/5.0/help/

4. Switch to Windows - Boot Camp: Set the default operating system.