If you want a easy web interface to the graphs there is a collectd-web package there but, that package, is actually the collection3 frontend. So, if you prefer the original collectd-web, then you will need to install it from its github site. The most important will be to create the /etc/collectd/collection.conf file. Be careful, if you want to change the path you will need to modify the sources.
The collection file content for CentOS is something like:
datadir: "/var/lib/collectd/"And a minimal configuration for the Apache would be like: