By default, you should be able to open an XLSM file without an issue (as long as you're using Excel 2007 or later), but the macros normally aren't enabled by default.

The Open XML format files are smaller than previous file formats. An Excel Workbook 2007 or 2010 business file enhanced with macros will have the XLSM file extension.

Excel files that support macros are XLSM files. How to Open an XLSX File Unless you've purposely installed a program to your ...