Given the problem that you want to put one or several logos in your document header, I found the following solution. All the lines have to be inserted in the document preamble, meaning before the \begin{document} line. You will need your logos in the appropriate format (in most cases EPS, pdflatex requires PDF, PNG, or JPG) in your document folder. I will assume logo1.eps and logo2.eps are the file names for the two logos. You will also need the graphicx package to actually include your graphic files.

\usepackage{fancyhdr}
\pagestyle{fancyplain} % use fancy for all pages except chapter start