Hi Marilyn, (just noticed it was answered already, more detail anyway)
Manually, using the name box at the left of the address bar is a
shortcut to using Insert (menu), Define, Name, Define
you should be able to figure it out if you use the menu.
to delete a named cell range
Insert, Name, Define,
select the name you want to delete and use the delete button
to change an existing defined name
Insert, Name, Define
select the name and change its range (at the bottom), OK button
If you reselect the range you want and give it an existing defined name
the new definition will replace the old definition (try it)