SSH is strongly recommended but just in case if you need Telnet server…
In order to turn Telnet on make sure that you have install the telnet-server and telnet RPMs:
yum install telnet-server telnet
Make sure that disable = yes is changed to read disable = no.
Type following to enable and start service on port 23:
chkconfig telnet on
chkconfig xinetd on
service xinetd restart
Again, I recommend that you use SSH to connect to a system instead of Telnet for security purposes.