Changed domain name error

I unfortunately am new to the world of blogs, yet was made admin of an organization’s blog. I naively thought I could change the domain name, not understanding what it actually took to do so.

SO – I went under “settings” and in the domain/blog boxes I typed in the new domain and hit save. Whoops! Now the blog has none of its original layout/formatting, and the links all lead to the new domain, which is empty space. Also, I can’t log in anymore to the admin settings.

HELP! I just want to return the blog to its original domain, but I don’t know how to.