I assume you are working in WORD.
You have 11 rows created in a table in 1 column and you want to make 22 cells.
First make sure you have the Tables & Borders toolbar loaded - if not right click anywhere on top blank toolbar to select it.
The first icon on the T & B toolbar is a small pencil just take that and draw a line approximately down the centre of the 11 rows.
Now select the table and go back to the toolbar and you will see an icon 'Distribute columns evenly,
You could also start afresh and create a table with 11 rows and 2 columns!
Hope this helps