Is this file ordinary text file, or is in some kind of format e.g. PDF? If it is pure text, then LibreOffice Writer can open it. LibreOffice is “Swiss army knife” for opening all kind of text files. If you have plain text file then:
Start LibreOffice Writer.
Click on Open icon from toolbar or from menu File | Open.
In Open dialog select text file and on bottom there is selection where by default it is “All files”. Click on this “All files” drop-down menu and select “Text - Choose Encoding”.
Then click on Open button from top-right of the dialog.
Now additional dialog appears. From “Character set” data field select “Cyrillic (Windows-1251)” and OK button. If there is plain text, LibreOffice Writer should open file correctly with encoding you have selected.
Another way to open text file in Vim text editor, using specific encoding, is to type on terminal: vi -c 'e! ++enc=cp1251' file.txt
Just a warning, Vim is not the simplest to use file editor. But if you want just read text, then it may be fine for you.