Displaying text in English AND Russian

I’ve searched forever to find the info on how to do this but so far, no success whatsoever.

I’ve looked at all the so-called help files on installing a Cyrillic .mo file but there’s absolutely nothing on having both (aside from the fact that the page where all the different languages are meant to be kept has only a handful of really obscure languages on it).

So where is the Russian .mo file and assuming I can find it, do I add it to define(‘WPLANG’, ‘en_GB’); because if I replace this then I’ve lost the English!

As usual, finding info here is like pulling teeth.

BTW, I’m on Alpha 4.0 of WP for some reason. I never requested it.