Install the language pack for the desired language:
Open the section "Site administration → Language → Language packs» («Administration → Tongue → Language packs»).
The list “Available language packs» («Available language packs") Select the desired language and click"Install selected language pack(s)» («Install the selected language pack»).
Configure the default site language:
Open the section "Site administration → Language → Language settings («Administration → Tongue → Language settings»).
In field "Default language» («Default language") Select the desired language and click"Save changes» («Save changes»).
Configure the admin panel language for the current user:
Open the user menu (in the upper right corner) and click “Preferences» («Settings»).
In the block "User account» («User account") Click"Preferred language» («Preferred language»).
Select the language you want and click "Save changes» («Save changes»).
from 2-00 to 7-00