btmiller is right, ssh is more secure than telnet. However, if your Linux box is not connected to the net (in other words, only the 5 machines on your network can connect to it), then you can probably live with telnet.
I haven't used Red Hat EL, but I imagine it shares some features with plain Red Hat (which is what I use).
If your linux box uses a gui:
Click to bring up the main menu -> Server Settings -> Services
Scroll through until you find a telnet checkbox. If it's not listed, then you'll need to install the telnet software
To install telnet software:
main menu -> System Settings -> Packages (or add/remove software)
Scroll down, select the detail button for the "Servers" group, and select telnet or telnetd
The software will be installed. Now, go back to the Services window from before. There should be a box for telnet now
Make sure the telnet box is checked. With telnet selected, click the "Start" button at the top of the Services window.
Click "Save" and now the telnet server will be started everytime you start up the computer
If your linux box is command line only:
You should be able to access the Services setting with redhat-config-services. I believe it has a command-line counterpart to the GUI tool.
Similarly, you can run redhat-config-packages to handle the software installation.
You can follow the above steps almost to the letter to install and setup ssh as well.