First click new and enter the following settings:
I named it OSX 10.9, and chose Mac OSX and Mac OS X 10.9 Mavericks (64 bit). Chose the appropriate one for you. Click Next.
Give it a certain amount of RAM. I advise at least 2500 for OSX but don't go above half your available memory.
The following settings should all be default:
First chose Create a Hard Drive now.
Chose the top one.
Chose dynamically and then chose at least 10GB (I went for 15. You need a lot for Xcode - 30+).
Untick all but CD/DVD and then move it to the top with the arrow keys.
Untick Enable EFI (special OSes only).
Click Display, and give it 16MB Video Memory (if you can). It has to be at least 8.
Click storage and then the Plus CD icon.
Click Chose disk.
Navigate to your OS X .iso file. It needs to be Hackintosh. I got mine from here. You have to disable adblock to get to it. (I used a torrent so it downloaded quicker - it is 5.5GB)
It is legal, but against what apple like you to do (as Mavericks is now free you don't need to pay anything. You can purchase an OSX 10.8 licence if you want, to make sure you are covered).
Click start and you can boot it.
Press Enter, and follow the installation process.
Complete the installation process. Then go back to Settings -> System -> Boot order, and disable CD/DVD and enable Hard Drive and move it to the top.
It will boot correctly. Finally, open the app store and install XCode from it (it's free).