I think he has connected the LEDs to a separate power supply.
This has nothing to do with the power adapter of the 3d printer.
But if you want to connect the LEDs to the 3D printer, it will certainly go.
For this you have to look at the connections at your power supply.
If a V+ and a V- connection is still free, you can connect the LEDs there.
It is important to note that these are 12V LEDs.
Here is a picture: