Using a Remote Control (which you need)

[davepl]

You need two things besides the mesmerizer board itself: the IR receiver dongle:
https://amzn.to/3P74wwT

And the actual remote control, which you'd be surprised is common enough you might have one already:
https://amzn.to/42BfM7E

Once you've plugged the dongle into the IR port, the remote should work. You can test it by using the UP/DOWN buttons on the very top right of the remote. They should change the effect. The FADE button will turn the VU meter off and on. The color buttons usually customize the effect color, but not for all effects.

The ON button pins the current effect. It also sets max brightness. The OFF button dims the display one step with each push. Press ON to make it bright again.

That's about it! If you have the matrix now, be sure to get the remote, as it's the primary way of interfacing and testing it.