documentclass[preprint,12pt]{elsarticle}
usepackage{epsfig}
usepackage{subcaption}
captionsetup{compatibility=false}
%% The amssymb package provides various useful mathematical symbols
usepackage{amssymb}
usepackage{mathptmx}
usepackage{amsmath}
newtheorem{thm}{Theorem}
newproof{pf}{Proof}
DeclareMathOperator*{argmin}{arg,min}
DeclareMathOperator{sign}{sign}
journal{X}

begin{document}

begin{frontmatter}

title{The title of the paper are placed here}


author{author1}
ead{author1_ family@yahoo.com}

author{author2corref{cor}}
ead{author2@yahoo.com}

author{author3}
ead{author3@yahoo.com}

address{The affiliations and adresses}
cortext[cor]{Corresponding author}

begin{abstract}
%% Text of abstract
Some text are presented here.
end{abstract}

begin{keyword}
%% keywords here, in the form: keyword sep keyword
Keyword1 sep Keyword2 sep Keyword3

end{keyword}

end{frontmatter}

section{Introduction}
label{intro}
Introduction goes here.

bibliographystyle{elsarticle-num}
bibliography{Bibiliography}
end{document}