\documentclass{article}

\usepackage{fontspec}
\setmainfont{TeX Gyre Pagella}

% Try to load a font by name.
% At the moment, this searches the system font cache,
% and thus usually fails.
%
% Eventually we'll implement support for that in Tectonic:
% we should check the bundle for ALL fonts, even those loaded
% by name.

\begin{document}

    \section*{Introduction}
    This is Introduction

\end{document}