Comment 9 for bug 1479907

Nikita, It is there, but the UI is quite succinct, but based very closely on the upstream design.

Goto the Region & Language panel, click Language. The first list of languages shown are the installed ones, click the "more" item (the three dot icon), you get an "Install Language", Select a language from this and you will get a popup to install the language packs.

There is one caveat and that is that if dpkg/apt are locked, because you have for example synaptic or similar open, then the code just times out, the initial implementation that landed in 15.10 can't detect this case, however we are looking to make a few improvements to this feature during the 16.04 cycle.