Give us back Steven Seagal, and we'll talk!
My guess would be...
1) Open the Q64 IDE
2) Click the "Options" tab.
3) In the menu that opens, lick the "Language" tab.
4) In the menu that opens,scroll down and highlight: MICSOFT_WINDOWS_CP1251
5) Click OK.
According to the QB64 Wiki:
http://www.qb64.org/wiki/Code_PagesCP1251 is stated as the unicode used for Russian.
I hope that helps, but I'm sure if it doesn't, someone else will be along shortly with a better answer. I've never used the language option, so I can't be sure my approach is the correct one.
Welcome to the forum,
Pete