In Openoffice it's easy to add or delete rows and columns from a spreadsheet. To insert a row, select a row then select Insert>rows from the menu.

If you want to delete a row. Select the row. Then click the right mouse button to display the popup menu. You will see a delete rows option and a delete contents option.

If you want to clear the row of its contents but leave the row in place, select the delete contents option.

In this example we want to delete both the contents of the row and the row itself so we will select the delete columns option.