Fcitx is in Ubuntu offical repo for a long time, but recently get synced with Ubuntu.
Since Ubuntu 12.04, it will have up to date Fcitx. If you want to install update to date Fcitx and related package, you can try to use ppa.
sudo add-apt-repository ppa:fcitx-team/nightly
sudo add-apt-repository ppa:fcitx-team/stable
to use different repository, you can browser two repositories via link before to make sure which version Fcitx it have.
After you add the repository, you can use
sudo apt-get update
or simply use your favorite package manager to do this, search fcitx and install it.