You can set only one default language for your tablet, but you can set multiple languages used for the on-screen keyboard.
To change the default language
From the Home screen, tap Apps
(in the Quick
Access Bar) > Settings 
> Language and input > Language >
tap the language you want.
To add additional languages for your keyboard
From the Home screen, tap Apps
(in the Quick
Access Bar) > Settings > Language and input. Tap the Settings icon 
to
the right of LG Keyboard, tap Input language and type, then checkmark the languages you want the keyboard to be able to
use.OR
Open the Notifications Panel (when an app that allows text input is open), tap Choose input method > Setup input methods > the Settings icon
to
the right of LG Keyboard > Input language and type, then checkmark the languages you want to be able to use.