using EmptyFlow.SciterAPI;

var sciterFolder = Environment.CurrentDirectory; // you need specify folder where will be located sciter library file (sciter.dll/libsciter.so/libsciter.dylib)
var host = new SciterAPIHost ( sciterFolder ); // create host and load API
host.EnableDebugMode(); // enable debug mode
host.EnableFeatures(); // enable all feature by default, or you can pass you set via parameter
host.CreateWindow ( asMain: true ); // create window (asMain mean pointer will be store in host.MainWindow property, instead you need to store it youself via returned variable)
host.AddWindowEventHandler ( new SciterEventHandler ( host.MainWindow, host ) ); // create and register window Event Handler (via event handler you can handle events from windows or elements)
host.LoadFile ( "file://path/my.html" ); // load HTML page, path specified in first argument
host.Process (); // start sciter and run main loop for show main window

public class MyWindowEventHandler : SciterEventHandler {

    public MyWindowEventHandler ( SciterAPIHost host ) : base ( host.MainWindow, host, SciterEventHandlerMode.Window ) { // define event handler with mode Window (which mean events will be handled from all elements on page)
    }

    public override void BehaviourEvent ( BehaviourEvents cmd, nint heTarget, nint he, nint reason, SciterValue data, string name ) { // handle behaviour events
        if ( cmd == BehaviourEvents.DOCUMENT_READY ) { // if document become ready, which mean it fully loaded
            var appDiv = Host.MakeCssSelector ( "#app" ).First (); // find tag with attribute id=app
            Host.SetElementHtml ( appDiv, "<b>Bold Text!!!!!!!!!!!!!!</b>", SetElementHtml.SIH_REPLACE_CONTENT ); // change html in these tag
        }
    }
}