If the telnet connection you want to use is in your Connection Directory, the following command line will start Procomm in telnet mode and make a connection to the telnet system:
pw5.exe connect telnet entryname
where entryname would be replaced by the name of the Connection Directory. If you are running a version earlier than 4.8, replace pw5.exe with pw4.exe
If the remote system is not in your Connection Directory, you can use:
pw5.exe connect manual telnet "address"
where address is either the IP address or fully-qualified domain name of the system you are trying to telnet to, and must be contained in quotes.