Add text above spreadsheet

A spreadsheet in Numbers is a document. A document contains sheets (tabs) and sheets contain tables, charts, and other objects. Do you mean a table?

Why not just create a text box as you have done, hide the table name (Format and uncheck 'Title' in the Table tab in the panel at the right) and place the text box right above the table that so it doesn't overlap it?

SG

The text box will not make the table move. But you can move the table yourself. Select it and drag from the circle at the top left of the table.

You will not be able to fit a text box between the table title and the header row unless it is really really small print. SGIII suggested turning off the title for the table. Put the table title in the text box along with the other text you want. Format the different pieces of text as you like, center the title, make it a larger font, etc. until it all looks like what you want.

You wrote:" What's the best way to enter a few lines of explanatory text at the top of my spreadsheet?"

You might consider using the CAPTION for entering a few lines at the bottom of each table. The CAPTION provides a perfect fit to each table.

Paul.