How to create custom rules for Sonar C# engine?

We want to add custom rules for our Unity 3D project. As far as we see Codacy uses Sonar C# engine for our code. We already reviewed GitHub - SonarSource/sonar-dotnet: Code analyzer for C# and VB.NET projects but we couldn’t find step-by-step tutorial for Codacy.
Please suggest.
TIA, Vitaly