This is primarily a Windows population here and also, there are several
Mac versions. But to answer your question, have you tried looking up
"Freeze Panes" in Help?

Curious wrote:

I use a Mac but have used Office extensively on DOS & Windows. The "Freeze
Panes" function was always great to use but in the Mac spreadsheet I'm using
it is not available as a selection. Is there something wrong with the way I
am using it, or is it just not available in the Mac version?