Uncyclopedia was a wiki completely separate from wikia.com until a few years ago so it works differently. The login names are completely different, but you can start an account there under the same name though if it's available. My name for both mainstream wikia.com and uncyclopedia is Miley Spears, but I had to sign up for each separately.
If you need help, feel free to leave me a message; you may also want to visit the forums or join us on Chat. You can also check the staff blog to keep up-to-date with the latest news and events around Wikia.