If anyone needs the solution, following this post solution, as follows :
G4FieldBuilder *fieldBuilder = G4FieldBuilder::Instance();
//Defining local field parameters
auto localFieldParameters = fieldBuilder->CreateFieldParameters("logicDetector");
localFieldParameters->SetFieldType(kElectroMagnetic);
localFieldParameters->SetEquationType(kEqElectroMagnetic);
//Using field builder to set up the field
fieldBuilder->SetLocalField(elField, logicDetector);