With that relay (and most others like it), you give it the same 5V power input that it outputs. That means you need some separate device to convert the PDP’s shaky 12V (+/-) to a steady 5V source. You can do this either using the 5V power supply on the VRM, or a separate 12V->5V step-down converter. I would highly recommend using a separate converter, as the VRM can only supply 2A max (which is not a lot for an LED strip) and to make sure you don’t interfere with the VRM’s most important job: providing power to the radio.
(I imagine you know this Gus; I’m saying this for the OP so they don’t accidentally put 12V into a 5V relay or fry their VRM)