First run the installer and install the RAC to standard winamp folder like proposed. If complaining about a non found file of winamp, just ignore and press proceed.

After finishing the installer start Winamp. In Winamp use the context menu Options>Preferences or press Ctrl-P to open the Preferences Dialog, then go to DSP/Effect, select

"Nullsoft Signal Processing Studio DSP vx.xx (dsp_sps.dll)"

and press "Configure active plug-in"-button.

Click "Load", point to "RAC 0.2.5.sps" or "RAC 1.1.sps" depending on your installed version and load.

Switch '[] Enable processing'
to '[x] Enable processing'!

Lay down the remote, lean back and prepare to enjoy.

Done!