Help installing webmin

I am a newbie to Trixbox and Linux. I can’t install webmin in Trixbox 2.6.1.13. I tried “yum –y install webmin”.

This is the output I receive after executing the command:

Loading "fastestmirror" plugin
Loading mirror speeds from cached hostfile
* trixbox: yum.trixbox.org
* base: centos.mirror.nac.net
* trixboxaddons: yum.trixbox.org
* updates: mirrors.greenmountainaccess.net
* addons: mirrors.unbornmedia.com
* extras: mirrors.unbornmedia.com
trixbox 100% |=========================| 1.1 kB 00:00
base 100% |=========================| 1.1 kB 00:00
trixboxaddons 100% |=========================| 951 B 00:00
updates 100% |=========================| 951 B 00:00
addons 100% |=========================| 951 B 00:00
extras 100% |=========================| 1.1 kB 00:00
Excluding Packages from CentOS-5 - Base
Finished
Excluding Packages from CentOS-5 – Updates
Finished
Excluding Packages from CentOS-5 - Addons
Finished
Excluding Packages from CentOS-5 - Extras
Finished
Setting up Install Process
Parsing package install arguments
No package webmin available.
Nothing to do

Thanks in advance.