To insert a row in your table, use one of the four insert buttons in the Rows & Columns area of the Table ribbon bar. These will insert a column or row in the direction you wish, based on what column or row you have selected in your table. Alternately, you can right click on the table, and in the context menu hover over insert, and choose from the same option list.

To remove a column, use the Delete button the Rows & Columns area. A drop down menu will allow you to choose to delete a row, column, or the entire table. You may also choose these options in the right click context menu under the Delete drop down menu.