Step 1: Add Ubuntu-VN repository, Open terminal, and use this command: 

$sudo add-apt-repository ppa:ubuntu-vn/ppa

Step 2: Update your system. Use the command: $sudo apt-get update.

Step 3: Install Ibus in your computer. Use the command: 

$sudo apt-get install ibus-unikey.

Step 4: In order to start iBus automatically startup. Use the command: 

$/usr/bin/ibus-daemon -d.

Reboot or logout your system, if ibus doesn’t start, use these command: 

$export GTK_IM_MODULE=ibus

$export XMODIFIERS=@im=ibus

$export QT_IM_MODULE=ibus