Figure reference
Examples for a single-column document. Replace the PDF filenames with your own image paths.
Required packages
Add these to the preamble, before \begin{document}:
\usepackage{graphicx} % Include images
\usepackage{subcaption} % Add subfigures and individual captions
\usepackage{float} % Enable the [H] placement option
One image
\begin{figure}[H]
\centering
\includegraphics[width=0.8\linewidth]{figure.pdf}
\caption{Description of the figure.}
\label{fig:single}
\end{figure}
Change 0.8\linewidth to adjust the image width; \linewidth fills the available line width. Place \label after \caption, then reference the figure with Figure~\ref{fig:single}.
Two images side by side
\begin{figure}[H]
\centering
\begin{subfigure}{0.48\textwidth}
\centering
% Here, \linewidth is the width of this subfigure
\includegraphics[width=\linewidth]{figure_left.pdf}
\caption{Description of the left image.}
\label{fig:left}
\end{subfigure}
\hfill % Leave space between the two images
\begin{subfigure}{0.48\textwidth}
\centering
\includegraphics[width=\linewidth]{figure_right.pdf}
\caption{Description of the right image.}
\label{fig:right}
\end{subfigure}
\caption{Two images in one row in a single-column document.}
\label{fig:two_figs}
\end{figure}
Each subfigure takes 48% of the text width, leaving room for \hfill between them. Keep the two subfigure widths below the total available width and avoid a blank line between the subfigures, which would start a new paragraph.
Use Figure~\ref{fig:two_figs} for the whole figure, or Figure~\ref{fig:two_figs}\subref{fig:left} for the left panel, typically shown as “Figure 1(a)”.
[H] places the figure at this point in the text rather than letting it float; it requires the float package. If there is not enough space, the figure moves to the next page and may leave a gap. In a two-column paper, use 0.48\linewidth for two panels within one column. To span both columns, use figure* with [t] instead of [H]. Check the paper template’s caption requirements before adding subcaption.