Xamarin.Forms.Carousel repo contains an alpha Xamarin Forms build enviroment. Similar to other .NET foundation repos (e.g. coreclr) everything starts in a shell. From there you'll need to build (or at least restore nuget packages) before opening the solution. The next generation build environment is being developed in the xfproj branch. For now the following commands should get you off the ground:

1. open cmd.exe using this link
2. ensure git.exe is available from the launched shell
3. type sln

1. close all instance of Visual Studio
2. open cmd.exe using this link
3. type killusual
4. type git status to ensure repro has no open or untracked files
5. type nuke to use git clean to restore repo to a clean state
6. type src
7. type rbuild to build a release package (just build for debug)
8. Your nuget package will be at bin\bld\release\carouselView\nuget\Package\Xamarin.Forms.CarouselView.2.3.0-pre2.nupkg