Boot Using OPTION key:
1. Restart the computer.
2. Immediately after the chime press and hold down the "OPTION" key.
3. Release the key when the boot manager appears.
4. Select the desired disk icon from which you want to boot.
5. Click on the arrow button below the icon.
Open Startup Disk preferences, select your startup volume, quit System Preferences.
Now if you have installed the Boot Camp utilities for Windows that you downloaded then a Startup Disk control panel was installed in Windows. It functions similarly to the OS X one. If you want OS X to be your permanent default system then leave Startup Disk where it is and use OPTION booting to boot Windows.