\documentclass{letter}
\signature{Joshua Naranjo\\
           Department of Statistics\\
           Western Michigan University\\
           Kalamazoo, MI 49008}
\begin{document}

\begin{letter}{Elizabeth Diaz\\
        131 River Street\\
        New City, Nevada 55555}

\opening{Dear Miss Diaz,}

Greetings.  I am pleased to inform you that your
application for admission has been approved.

Congratulations.


\closing{Sincerely,}
\end{letter}
\end{document}