Before you install the Nagvis prerequisties, do install the following:
1. Install mySQL database
# yum install mysql mysql-devel mysql-server gcc-c++
2. Install PHP and required PHP modules
# yum install php* php-gd php php-mbstring php-mysql
It is useful to install NDOutils as Nagios' NDOutils store all configuration and event data from Nagios into a database, which will help facilidate quicker retrieval and processing event data. Lots of other Nagios-related tools (e.g. NagVis rely on the MySQL backend made available by NDOUtils. Do refer to this excellent article NDOutils on CentOS
3. Compiling Nagvis on CentOS 5.x
Finally, here the unfinished portion, first go to Nagvis Download site
Untar the Nagvis package and install
# tar -zxvf nagvis-1.5.1.tar.gz
# cd nagvis-1.5.1
# ./install.sh -B /usr/bin/nagios
You want to take a look at Install and Configure NagVis although the instruction is for Debian Derivative