How to locate figures with x,y specified location in a presentation

You could use the textpos package for absolute positioning of figures or text boxes.

Here's an example:

\documentclass[demo]{beamer}
\usepackage[absolute,overlay]{textpos}
  \setlength{\TPHorizModule}{1mm}
  \setlength{\TPVertModule}{1mm}
\begin{document}
 \begin{frame}
   \begin{textblock}{20}(40,20)
      \includegraphics{file}
    \end{textblock}
 \end{frame}
\end{document}

with the syntax \begin{textblock}{*width*}(*x-position,y-position*)

As far as I remember,

\usepackage{tikz}
\usepackage{graphicx}
\usetikzlibrary{calc}

...

\begin{tikzpicture}[remember picture,overlay]
  \node[anchor=south west,inner sep=0pt] at ($(current page.south west)+(2cm,5cm)$) {
     \includegraphics{imgfile}
  };
\end{tikzpicture}

should place imgfile.pdf at x=2cm and y=5cm from the lower left page corner.

As suggested by @PalaniKannan you could do the following:

\begin{picture}(50,50)
\put(200,-300){\hbox{\includegraphics[scale=0.3]{file}}}
\end{picture}

This will place the image at position "200 right and 300 down" relative to the top left corner of the current page.

Also have a look at this wiki page.