To compile the project, you need to install the .NET Core tools from here (The download labeled "Install the .NET Core tools preview for Visual Studio").
Afterwards, run dotnet restore in the base directory.
The selected launch configuration can be changed in debug view (Ctrl+Shift+D). Afterwards, build and start by pressing F5.
If you want to build without running, use either the default build target (Ctrl+Shift+B), or select a target using the command palette.
For building, run dotnet build followed by Backend and/or Bots in the base directory.
Run the executables by either calling dotnet run inside the respective project directory, or by calling run.bat which starts both the backend and the bots.