After you Import the Publish settings file , to know how to do this, check this post
you first run this command in Windows Azure PowerShell Command:
it will prompt for you to enter the name of the subscription, which you can get by running
you type in the name of the subscription and then run this command to set your subscription as default.
it will prompt for you to enter your subscription name again, please enter the same subscription name you entered at the beginning and then you will be able to see the screenshot below which indicates that you have a successful operation.