There is no such model as a 5565 or 565.
That aside, one enables telnet via the command:
telnet <source address> <netmask> <source_interface>
...filling in your local information for each of the bracketed fields. For example:
telnet 0.0.0.0 0.0.0.0 inside
...would allow telnet for any host via the inside interface.
Reference.
Note that it is recommended to NOT use telnet to access a firewall as you would be using an insecure access method to access a security appliance.
