\documentclass[10pt,a4paper]{article}
\usepackage{graphicx}

\begin{document}
\begin{center}
\includegraphics[scale=.6]{../REF/Screenshot_2021-04-13_12-28-25.png}   
\includegraphics[scale=.6]{../REF/Screenshot_2021-04-13_12-28-54.png}   
\includegraphics[scale=.6]{../REF/Screenshot_2021-04-13_12-29-18.png}   
\includegraphics[scale=.6]{../REF/Screenshot_2021-04-13_12-29-37.png}   
\end{center}
\end{document}