Help:Introduction to tables with VisualEditor/4
Introduction to tables
How and why
Adding new tables
Much easier than it used to be
Adding rows and columns
Review of what you've learned
To add a column or row, you need to define where you want to insert it. Once you've selected a cell, a triangle will appear at the top of the column, and the left of the row.
Clicking on the top triangle allows you to add a new column before or after the selected one (or delete it). Similarly, clicking the left triangle allows you to add or remove rows.