womenonwalls on "Changing Spelling of Domain Name"

Hi: I purchased the domain name upgrade for my blog, but forgot to add a letter. The domain name i purchased was womenonwall.org, but i would like to change it to womenonwalls.org. I forgot to add the "s", so how do i changed the spelling of a purchased domain name so that it appears in the address bar as womenonwalls.org?

Thanks,
Angie