\documentclass[11pt]{article}

% Imports %
\usepackage{amsmath}
\usepackage{graphicx}
\usepackage{subcaption}
\usepackage[export]{adjustbox}
\usepackage{tcolorbox}
\usepackage{xcolor}
\usepackage[utf8]{inputenc}
\usepackage[a4paper]{geometry}

\addtolength{\oddsidemargin}{-0.5in}
\addtolength{\textwidth}{1in}
\addtolength{\evensidemargin}{-0.55in}
\addtolength{\topmargin}{-0.75in}
\addtolength{\textheight}{1.5in}

\begin{document}

\begin{tcolorbox}[colback=gray!5!white,colframe=black!75!black,title=Your Ticket - libreevent event management solution]
\vspace{6cm}
\end{tcolorbox}

\end{document}