WHM (root) > Theme Manager > Language > Selectable Languages

We currently support 24 languages on RVskin control panel to be chosen as your favourite choice. You can set language that you will provide to clients in "Selected Languages", then your client can choose as they want. This feature can attract your customers and extend the international market coverage. English is somewhat a medium language as a world standard usage for all nationalities BUT not all. So, it'd be better to widen your control panel languages to serve worldwide clients i.e. Arabic, Brazilian-Portuguese, Bulgarian, Dutch, Finnish, French, German, Greek, Hungarian, Indonesian, Italian, Japanese-euc-jp, Japanese-shift_jis, Korean, Norwegian, Polish, Romanian, Russian, Simplified-chinese, Slovenian, Spanish, Swedish, Traditional-chinese, and Turkish.
In "Selectable Languages" from WHM
Set provide the available languages for clients
End-user interface in Russian