If you have two Ones, you can add them as surrounds to the Beam by following these instructions:

https://support.sonos.com/s/article/2927?language=en_US
 

If you just have one Sonos One, you can group it with the Beam by following these instructions:

https://support.sonos.com/s/article/3391?language=en_US

You cannot add a Sonos One to a Beam as a single speaker. You can PAIR a  Sonos One to a Beam to enjoy the same music on both. For it to work the Beam and Sonos One must be setup as separate rooms. This procedure is not recommended to send TV audio to a Sonos One as there will be a 75ms delay to the Sonos One speaker.

You can however BOND two Sonos One’s as surround speakers to a Beam in a home theater setup. The Sonos One’s when used as surrounds will no longer be visible in the Sonos app as individual speakers nor a stereo pair.?

Oh well…looks like @GuitarSuperstar is a faster typist than my hunt and peck method on my iPhone