\documentclass[12pt]{article}
\usepackage{amsmath}
\usepackage{authblk}
\usepackage
[
  a4paper,% other options: a3paper, a5paper, etc
  left=2cm,
  right=2cm,
  top=2cm,
  bottom=2cm,
  % use vmargin=2cm to make vertical margins equal to 2cm.
  % use hmargin=3cm to make horizontal margins equal to 3cm.
  % use margin=3cm to make all margins equal to 3cm.
]{geometry}

% add packages and define new commands/envs between here and \begin{doc...}

\begin{document}

\title{}
\author[1]{Author \thanks{Email: example@email.org}}
\date{\today}
% \date{21 Januari 2010\\\small{(Edisi Revisi : 3 Januari ,! 2019)}}
% \affil[1]{\small{Hyang Language Foundation, Jakarta, ,! Indonesia}}

\maketitle

\begin{abstract}
\end{abstract}

\tableofcontents

% If you want citations, add "biblio.bib" and uncomment below
% \medskip
% \bibliographystyle{unsrt}
% \bibliography{biblio}

\end{document}