Apart from Virtual Box, to install Mac OS X, you will require OSX86 ISO. There are tons of torrents, which will fulfill your requirement. But we would recommend you to buy original Mac OS X for safety and security reasons. It is upon your discretion, whether to contravene copyright laws, or be a law-abiding global citizen, by purchasing the copy. After you have got all the requisite items. The steps are as follows:

1. First install Virtual Box on your hardware, then launch the application. Click on ‘New’, at the top left.

Step 1 : Click on 'New' button.

2. When ‘Create New Virtual Machine’ window pops up, give your desired name to this Virtual Machine, in the label field of ‘Name’. From the drop down menu, select ‘Mac OS X’, as your operating system, while the version as ‘Mac OS X Server’. Then, click ‘Next’ and proceed to next step.

Step 2 : Name your VM and selection of OS and its Version.

3.  The next windows that pops up, will ask you how much to sanction ‘RAM amount’. You can drag it as much as you wish, but 1024 MB would be enough. Then proceed to next step by clicking ‘Next’.

Step 3 : Assign RAM amount

4. Now the most crucial part in the whole procedure, allocate the part of your hard disk. Allocation for 20GB is sufficient. I would suggests you not to opt for ‘Dynamic’ option, as many people tend to end up messing.

Step 4 : Allocate Hard Disk Size

By clicking ‘Next’, you will shown ‘Summary’, if you are satisfied, then click ‘Finish’. Then proceed to the following step.

5. Now click on the ‘Settings’ on the top. Within this windows, on the left pane, click on ‘System’, and uncheck "Enable EFI”.

6. Within the same window, on the left pane, select ‘Storage’, and then select ‘Empty’, under the file ‘YourVMName.vdi’.

Step 7 : Select 'Empty' under IDE Controller

7. Click on the ‘Add’ button. Then add your OSX86 ISO, if you have downloaded the torrent. If you have bought the CD, then extract from it the ISO file. ‘Select’ it and then click ‘OK’, and hit the ‘Start’ button on the left side of the main VirtualBox window.

Step 7 : Select ISO image of OSX86

8. As soon as the VM Booting start, hit ‘F8′ and type ‘-v’ at the the boot prompt. This will enable you to detect any shortcomings or if anything goes wrong.

After a while, a pop up window will appear, select your preferred language. Then click ‘Next’.  Then, click ‘Continue and Agree’. And start up ‘Disk Utility’ by going to ‘Utilities’ in the menu bar.

Step 8 : VM Booting

9. (a) Select then "20 GB VBOX HARDDISK”. Now type your desired name, in the ‘Name’ field, after doing this click on ‘Erase…”. After this has been done, quite the ‘Disk Utility’.

Step 9 (a) : Name your VM

(b) Now select the Hard Drive, and click ‘Continue’.

Step 9 (b) : Select the Hard Drive

10. (a) Click on ‘Customize’ at the bottom left, and check the following:

For AMD Users: 

• Any Updates included at the top.
• Drop down Kernels and choose Legacy kernel.
• AMD option below System support.

For Intel Users: 

• Any Updates included at the top.
• Drop down bootloaders and check the newest Chameleon.
• Drop down Kernels and choose Legacy kernel.

After being done with this, click ‘Done’ and strike on the ‘Install’ button, to initiate the installation.

(b) On the very moment, when the installation is finished. And starts the countdown for restart. Press right ‘Ctrl’.

Step 10 (b) : Chameleon Loader

Now click ‘Devices’,  at the top of the VirtualBox window, hit ‘CD/DVD Devices’ and the strike for ‘Unmount CD/DVD Device’. Then go to "Machine > Reset” and click "Reset” at the prompt. Now you’ll see the Chameleon loader and then OS X will begin to boot.