Wyam uses Cake to handle scripted build activities. Right now, Wyam is Windows-only (both build and execution). If you just want to build Wyam and all the extensions, run
build.cmd
If you want to build and run tests, run
build.cmd -target Run-Unit-Tests
You can also clean the build by running
build.cmd -target Clean
If you want to open and build Wyam from Visual Studio, the main solution is in src\Wyam.sln.
The src\Wyam.Windows.sln solution is only for the Windows-specific installer application and you'll probably never need to view or edit it.