I am writing my thesis by using isuthesis package. I want page numbers to come at the middle of bottom of the page. For that I thought of using fancyhdr package.

\documentclass[answers,a4paper]{isuthesis}
\usepackage{fancyhdr}
\begin{document}
hello world
\end{document}


I get the build error:

! LaTeX Error: Command \lhead already defined. Or name \end... illegal, see p.192 of the manual.

• presumably the thesis package you are using already has an lhead command for setting the heading, so you should use that. you'll need to look to its documentation – David Carlisle Sep 20 '14 at 14:03
• The isuthesis.cls from the Iowa State University can be obtained here: isuthesis.zip It does in fact define the \lhead etc. commands already. However, it seems in some portions to be outdated – user31729 Sep 21 '14 at 9:59
• I am not an expert in latex, so not able to understand documentation of .cls file well. Please suggest how to get page numbers at middle of the bottom of the page? – user961708 Sep 22 '14 at 5:25
• \cfoot{\thepage} without hancyhdr? – Symbol 1 Sep 26 '14 at 3:02

As stated in the comments, the class already defines commands like \lhead or cfoot, you can just use them.
\documentclass{isuthesis}