Follow the instructions below:1. First of all, download Oracle VM VirtualBox from here and Android x86 4.3 ISO file from here.
2. Install VirtualBox in your computer and run it.
3. Select NEW. A Dialog box will appear, Enter the name you wish for your OS and select Type as LINUX and version as OTHER LINUX and click NEXT.
4. Now choose the amount of RAM you would like for your virtual machine. Use at least 1GB for this step.
5. In the next step, select CREATE A VIRTUAL HARD DRIVE NOW and click CREATE button.
6. Now in the next step, select VDI and click NEXT.
7. Now set storage space for your OS as per your requirements and click CREATE button. I recommend 8 GB.
8. Now your virtual machine is set. All you need to do is add the location of the Android 4.3 image file. Click on the settings button in virtualbox. Under the settings navigate to storage, below the storage tree select empty and click on the disk image and select "choose a virtual CD/DVD disk file" and select the android 4.3 image. Check the Live CD/DVD box and click OK.
NOTE: You might need to enable virtualization in your computers BIOS. You can enable it from your PC’s BIOS as shown below.