To do Alt + W F R on Mac in Excel, download and install Accelerator Keys, then press Option, followed by W, F, R.
Command: Freeze Top Row
This is how to do Alt + W F R on Mac in Excel with Accelerator Keys, the native ribbon and alt key shortcut solution for Mac users who get more done with Excel.
Alt + W F R freeze Top Row keeps the top row visible while you scroll down. This is useful when your first row contains column headers.