Lertap5 is an Excel application. Your computer must be able to run Excel, the spreadsheet program from Microsoft, usually distributed as one of the applications in the software suite called "Microsoft Office". Other applications in this suite are Word, Access, and PowerPoint.
So? Excel. You need it to run Lertap5. Got it? Good. But note: your copy of Excel has got to be one which will "run macros". The version of Excel for the iPad is not capable of running macros. The various "mobile" versions of Excel, handy and powerful as they may be, are not capable of running macros either. (Macros are modules of computer code; Lertap 5 code is written in "VBA", Visual Basic for Applications.)
Do you have a Windows computer using Excel 2010, Excel 2013, Excel 2016, Excel 2019, or Excel 365, or a Macintosh using Excel 2016, Excel 2019, or Excel 365? If not, Lertap5 will not be for you (alas!).
Excel 365 is a version name used by Microsoft when a user has taken out an annual subscription to Office 365. As of April 2018, it referred to Excel 2016.