How can I add section numbers in this ACM template?

I have to use this LaTeX template for a uni report, however it does not contain numbered section headings, which I need.

So what I want is instead of

Example Section Title

I want

1. Example Section Title

\def\thepart{\Roman{part}} % Roman numeral part numbers.
\def\thesection       {\arabic{section}}
\def\thesubsection    {\thesection.\arabic{subsection}}
\def\thesubsubsection {\thesubsection.\arabic{subsubsection}} % GM 7/30/2002
%\def\theparagraph     {\thesubsubsection.\arabic{paragraph}}  % GM 7/30/2002
\def\thesubparagraph  {\theparagraph.\arabic{subparagraph}}

The whole template can be downloaded here

https://chi2020.acm.org/wp-content/uploads/2019/06/proceedings.zip

Thanks a lot!