On the File menu, click Open, and then click Project/Solution, and then browse to the project (.csproj or .vbproj) or solution (.sln) file that you want to open.
Select the project or solution file, and then click Open.
See Open a Silverlight 1.0 project.
See Open an existing Silverlight 2 project.
On the File menu, click Recent Projects. The ten most recently edited projects appear in a list.
Select a project from the list.
You can also open a recently edited project by using the Projects tab on the Welcome Screen (Help menu).