I've been using Numbers for Mac for quite some time but used to use Excel quite a bit. I remember it being quite simple to add a header row to a table. Now, after reading the help material, it seems that you have to indicate that you want a header row upon initial table creation. Now when I try to go back and add a header row, it's not letting me do so. I'm sure there has to be a logical and easy answer for this issue. I'm using the client. Can anyone provide insight?
It's not totally clear whether you're asking about an Excel table or a Numbers table. I'm going to assume you're NOW using Excel again. (I'm a Mac user myself, but since I have Excel as well, I can't imagine a reason to use Numbers unless it's to create something for somebody else who doesn't have Excel).
Anyway, I've just tried to create a table--you say you already have one--and Excel won't let me create it without headers. Excel creates headers for itself. Granted, the headers it puts in are generic, but they're headers. Making me wonder if what you have is really an Excel table, per se, or is it just a set of rows and columns. Here's what happens when I take a set of rows and columns and go through the Insert....Table from the Home tool bar.
And it would be very easy to change those header names to whatever you desire.