How to migrate an existing ASP.NET App to run on Windows Azure

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.NET4

Hi,
Im beginner to the Windows Asure Platform. I want to migrate the existing ASP.NET app to run on Windows Azure. I have searched in net and followed according to it but its not working. First I have created a new Windows Azure Project and I have right clicked on the solution explorer -> Add -> Existing Website. And To the Azure project Roles folder -> add -> Web Role to the Solution and select the web application. Here first of all Web Role to the Solution is not highlighting.

We have to add the existing website as it is a web application. But, in the examples that I have seen in net, they are adding as solution explorer -> Add -> Existing Project. When I follow according to it its not working. Im not understanding how to do it.
Is there any difference between website and web application? According to me both are same.

Thank you,