After installation of i3wm complete, it's time for install Chinese input method for ArchLinux.
$ sudo pacman -S fcitx fcitx-im fcitx-ui-light fcitx-libpinyin fcitx-sunpinyin
$ sudo pacman -S ttf-dejavu adobe-source-han-sans-otc-fonts
$ cat .xinitrc
...
export GTK_IM_MODULE=fcitx
export QT_IM_MODULE=fcitx
export XMODIFIERS="@im=fcitx"
...
$ sudo reboot
To verify, run fcitx in terminal, check if there is any warns or errors.
Then run fcitx-configtool. If there isn't input methods under "Input Method" tab,
run sudo pacman -S fcitx-cloudpinyin fcitx-sunpinyin fcitx-googlepinyin fcitx-libpinyin.
Ref: Fcitx on Arch Wiki.