When you enter the game, you are greeted by a menu in which you can select a module, as well as configure the game, so you need to go to the "Configure", and then in the "Language", change to the one you need, it’s simple.
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=3254848948
However the mod may not have the localization you need, "Civil War In Russia" mod supports the following languages:

The game does not have a built-in Russian translation in steam, so the only working way to fix this is to install a third-party Russifier from the author, here is this link