Look for the column selection tool (arrowed in the image below) in the WP ruler bar at the head of your WP document. Clicking on the split-box to the right of the number (of columns) increases the number, clicking on the single box to the left decreases the number.
I don't use Appleworks any more, but just looking at it quickly, on the spreadsheet you select the column where you want to add or insert one, then go under 'Format' > 'Insert cells'
I just see the post above - depends on which type of document you want to add columns.
Linear Mode
