% preamble
\documentclass[12pt]{article}
%\usepackage[text={5in,5in},centering]{geometry}
%\usepackage[margin=1.5in]{geometry}
%\usepackage[total={6.5in,8.75in},top=1.2in,left=0.9in,includefoot]{geometry}
\usepackage[english]{babel}
\usepackage[left=2.5cm, right=3cm, top=1.5cm, bottom=2cm]{geometry}
\usepackage{lipsum}
\usepackage{multicol}

% basic legnths:
\setlength{\parskip}{1cm} %
\setlength{\parindent}{0.3in}
\renewcommand{\baselinestretch}{1.5}
\setlength{\columnsep}{2.5cm}

%Body
\begin{document}
\section{Setting Lengths}
\label{sec:first}

\lipsum[1]

\lipsum[2]

\lipsum[3]
\newpage
\section{Spaces}\label{sec:spaces}

\begin{multicols}{2}
  [\subsection{Columns space}
    This is some text in just one column. However, the next text is in multiple columns.]
\lipsum[3]
\end{multicols}

\newpage
\subsection{Other kind of Spaces}
\label{sec:others}

Here are some special spaces, \hspace{3cm} like horizontal.\par
Also vertical space \hfill here. \vspace{1cm}


New paragraph.\par

\vfill

At bottom.

\section{Text alignment}
\label{sec:alingment}



\end{document}