you can't
no.
Go into your computer to Bill's PC, and then to "Move Pokemon". When you click on the box, one of the options should be to rename it.
You can rename a pokemon by going to the Name rater
there is no such thing as the name deleter but there is a person in eterna who will rename your Pokemon and in canalave there is the move deleter.
You should be able to rename a Pokemon any number of times in the game.
In slateport city there is a name rater who can rename your Pokemon remember Pokemon traded to you can't be renamed.
In Eterna city where the second (grass type) gym is, go into the apartment block and on one of the floors there is an old man who will rename your Pokemon. He will not rename Pokemon that you got in a trade though.
The Name Rater will rename any of YOUR Pokemon. If you own a Pokemon that originally belonged to someone else (Like the Machop you trade for in Goldenrod), then he wont rename it.
Go to the namerater in Lavender Town or rename it right after you catch it.
lavender town
In Eterna City, (the town with the second gym) beside the Pokemon shop, there is a building, go in and talk to the old looking man, then he will let you rename your Pokemon.
Just go to Exploration Record on the main menu and select Rename Team.