The easiest way is to use either eKeypad or whatever the Android equivalent is on your smartphone. If you're not running Android or iOS, then load up a home automation app like Premise or Elve or Homeseer or CQC and make a web-page you can access from your phone or computer.
If none of those options work, you can go old school and dial into the thing and control it through the built in IVR (interactive voice prompts). That's what people did before smartphones came along.