Entering name with aligned position/address below

Leaving aside the fact that there are classes for writing letters, the job of aligning material is most easily achieved with a tabular

\documentclass[12pt,a4paper]{article}

\begin{document}

\begin{tabular}{@{}l@{ }l@{}}
To: & John Smith \\
 & Position Here\\
 & Address here
 \end{tabular}

\end{document}

or maybe

\documentclass[12pt,a4paper]{article}

\begin{document}

To:
\begin{tabular}[t]{@{}l@{}}
John Smith \\
Position here\\
Address here
\end{tabular}
\end{document}

It's as simple as that :-)

Here shown with a \Longunderstack:

\documentclass{article}
\usepackage[usestackEOL]{stackengine}
\begin{document}
To: \Longunderstack[l]{John Smith \\ Position Here\\ Address Here}
\end{document}