Download the latest version here.
Extract the files and copy the /addons/ directory into /game/csgo/.
Modify /game/csgo/gameinfo.gi as such by adding Game csgo/addons/metamod:

FileSystem
	{
		SearchPaths
		{
			Game_LowViolence	csgo_lv // Perfect World content override

			Game	csgo/addons/metamod

			Game	csgo
			Game	csgo_imported
			Game	csgo_core
			Game	core

Installing CounterStrikeSharp

Download the latest version with runtime here.
Extract the files and copy them into /addons/.

Installing Porning

Clone the latest version of the repository.
Modify plugin.csproj by changing the directory used to copy the output files of the plugin.

  <Target Name="CopyAllOutputAfterBuild" AfterTargets="AfterBuild">
    <ItemGroup>
      <MyOutputFiles Include="$(TargetDir)**\*.*" />
    </ItemGroup>
    <Copy SourceFiles="@(MyOutputFiles)" DestinationFolder="$SERVER_LOCATION$/game/csgo/addons/counterstrikesharp/plugins/plugin/%(RecursiveDir)" />
  </Target>