uses iehttp3;
...
procedure TForm1.Button1Click(Sender: TObject);
var iehttp1: TIEHTTP;
begin
    iehttp1 := TIEHTTP.Create(nil);

    iehttp1.username := 'xxx';
    iehttp1.password := 'xxx';
    iehttp1.ExecuteURL('https://stat.biisk.ru/');

    showmessage(iehttp1.sl.text);
end;