How do I add a column ?

If you want to add a column to the right of the last column displayed, right click in the header of the empty column and in the context menu select the item to fill the column.

To insert a column between two existing columns, right-click in the column header to the right of the column you want to insert and choose the Insert Column command. A new column appears to the left of it. Right-click in the header of the new column and select the item to fill the column from the pop-up menu.