Have you yet performed "sudo apt-get update" and "sudo apt-get upgrade" ?
These two steps together usually cause Trisquel to download and install almost all available language support to a fresh installation of Trisquel unless one takes extra steps to avoid that result.
Alternatively, open Synaptic Package Manager, then type "language" into the search bar, then select "Search Results" and scroll down through the umpteen choices of language packs, selecting as few or as many that you do/do not want to be installed.
In my case, the task was to unselect all but my language of choice for a USB-Stick installation; your task my differ.
Afterwards, select "Apply" and Synaptic Package Manager will take it from there.
