You can use
# more specifically
to find out what version of RHEL you have.
By the look of the date in the version info, its quite old; may even be a v5.x, which is still supported by RH. v5.9 is just out recently.
You'll need to do a comprehensive backup before using yum to update it. It'll require a reboot as it'll have new kernel versions.
(Current latest & greatest is 6.3)
You can check the repo settings by looking in /etc/yum.repos.d dir.
Here are the Admin Guides http://www.linuxtopia.org/online_boo...ion_index.html
As mentioned above, RHEL is a paid subscription distro, so contact RH and/or your Mgr to get the subscription info, otherwise no updates or support will be forthcoming.
Ultimately if money becomes an issue, you could convert it to Centos, a free RHEL rebuild, but that only includes updates.
You'd have to support it yourself via Google, LQ, the Centos website etc.