documentclass[12pt]{report}
usepackage{suthesis-2e}
usepackage{graphicx}
usepackage{epsfig}
usepackage{amsthm}
usepackage{amsfonts}
usepackage{amssymb}
usepackage{tikz}
usepackage{pgfplots}
usepackage{caption}
usepackage{upgreek}
usepackage{subcaption}


newtheorem{theorem}{Theorem}[section]
newtheorem{remark}{Remark}[section]
newtheorem{definition}{Definition}[section]

begin{document}

begin{figure}
begin{center}
    includegraphics[scale=0.6]{myRandomWalk}
    end{center}
end{figure}

! Too many }'s.
! LaTeX Error: begin{document} ended by end{figure}.
! Extra endgroup.