Follow the instructions here on how to download and import the vm into virtual box
Once you have imported the vm select the vm and click on setting
Then click on network
To assign a IP in the attach to down drop list select "Bridge Adapter"
Then under option Promiscuous Mode select "Allow All"
Now start your vm
Once the machine is up verify you have a IP address
Now you have IP for your vm. have fun.
@Sunile Manjee nice article. Minor edit: the first screenshot should show Settings circled not Start.
@slachterman Good catch. fixed.