Start by telnetting to the printer's address and port 9100.
$ telnet 10.10.0.156 9100
Connected to 10.10.0.156.
Escape character is '^]'.
Note that the Escape character is generated by pressing Ctrl-]; the caret (^) means use the Ctrl key.
Type some text and then press Ctrl-L to eject the page, and the text you typed should be printed on the page. There is no wordwrap, so if you type more than about 80 characters on a line, they won't be on the page. On the other hand, hitting Enter as you type will cause the output to start on a new line (like a typewriter, basically).
To end the session, press Ctrl-] which will take you to a telnet> prompt, and then type quit.