Click the data tab on the top center ish
By default when you click a table on the left, you're seeing what is called the schema. (It's basically defining the types of fields in the table). When you click the data tab, you're now seeing the records inside your DB, and you can double click/edit fields by changing values, much like Excel.
Also, nerdgasm's note about the locked/unlocked may be slightly confusing, you can comment/uncomment the <locked/> element to enable locking.
Code:
<!-- Server status. Default is unlocked DO NOT EDIT RIGHT NOW -->
<!-- <locked/> -->
<!-- <unlocked/> -->
by removing the <!-- --> wrapping parts.