\documentclass{article}

\usepackage[english,russian]{babel}
\usepackage{fontspec}
\setmainfont[
    Path=./fonts/freefont/,
    Extension = .otf,
    UprightFont=*,
    BoldFont=*Bold,
    ItalicFont=*Italic,
    BoldItalicFont=*BoldItalic
]{FreeSerif}

\title{Some doc}

\begin{document}

\maketitle

Привет мир!!

\end{document}