Dealing with tables

Some time back I added a table to a page by copying and pasting from Word. Now I want to add a row to the table but can’t seem to do this from within WordPress. And I can’t add to the table in the Word and then repaste as I no longer have the Word table. I also can’t copy it from WP to Word and then edit it as when I try and do this, all the cell formatting is lost when pasting into Word. Any suggestions as to how to proceed?