The odds are telnet is not installed on your system. Telnet is not secure, sends plain text logon information across what ever network you try to log across. For this reason it will not be installed by default.
If you want to do remote log ons, then use ssh. It is secure, fully supported and can do things like secure file copying. You can forward X session data ( the gui stuff from an application ) as well.
You will find lots of information here
http://www.openssh.org/ on how to get started with ssh.
To answer your first question, you can find a file with the command 'find'. I would recommend you use the command 'locate'. Find looks through what ever path you specify, and can take a lot of time on a large system. Locate uses a database to give the path to a file. In order to use the database, you must update the database. That is done as root. On a konsole, become root. As root, run the command 'updatedb' ( without the quotes ). The first time will take some time to complete. After the database is built, log out of root. Then run the command 'locate telnetd' to find the path to the file. If you get no response, that means the file is not in the database you just created. ie, it is not installed.
If you have to use telnet, you will need to install it.
