There are two options for SignalRGB Compatible QMK Firmware: Pre-compiled Firmware & Building Firmware From Source.
Pre-Compiled SignalRGB Compatible Firmware is available for select keyboard models. Pre-Compiled Firmware is plug and play for supported keyboards. The list of supported keyboards and their download pages is here.
Building Firmware From Source:
If your keyboard does not have a pre-compiled SignalRGB compatible firmware file, or you want to make changes to the firmware file, then you will need to build your firmware from source.