I put together a little test here:
\documentclass[10pt,twocolumn]{article}
\title{Article Title}
\author{
First Author\\
Department\\
school\\
email@edu
\and
Second Author\\
Department\\
school\\
email@edu
\and
Third Author\\
Department\\
school\\
email@edu
\and
Fourth Author\\
Department\\
school\\
email@edu
}
\date{\today}
\begin{document}
\maketitle
\begin{abstract}
\ldots
\end{abstract}
\section{Introduction}
\ldots
\end{document}
Things to note, the title, author and date fields are declared before \begin{document}. Also, the multicol package is likely unnecessary in this case since you have declared twocolumn in the document class.
This example puts all four authors on the same line, but if your authors have longer names, departments or emails, this might cause it to flow over onto another line. You might be able to change the font sizes around a little bit to make things fit. This could be done by doing something like {\small First Author}. Here's a more detailed article on \LaTeX font sizes:
https://engineering.purdue.edu/ECN/Support/KB/Docs/LaTeXChangingTheFont
To italicize you can use {\it First Name} or \textit{First Name}.
Be careful though, if the document is meant for publication often times journals or conference proceedings have their own formatting guidelines so font size trickery might not be allowed.