//1.设置语言包路径
FastReport.Utils.Res.LocaleFolder = AppDomain.CurrentDomain.BaseDirectory + "Localization";
//2.设置想要的语言，这里Chinese (Simplified).frl对应语言包下的文件名
string chineseSimpleFrl = AppDomain.CurrentDomain.BaseDirectory + @"Localization\Chinese (Simplified).frl";
FastReport.Utils.Res.LoadLocale(chineseSimpleFrl.ToUpper());