Word, Excel, or PowerPoint) for both Mac and Windows users. Newer versions Office for Mac 2011 Apply a pre-defined cell border. Step 2 Click on Blank workbook to open a blank document in Excel. … Follow the below instructions, if you want to insert Σ symbol in Excel Mac version. After you restart Excel, the add-in should appear in the Add-Ins available box. Here’s a step-by-step guide on how to do this in Excel: Step 1 Open MS Excel. This article explains how to insert an Excel spreadsheet into a Word document. How to add character after the first character of cells in Excel. How to insert greek letters in excel mac Symbols” menu.