Can someone help me with this?

I'm using this diagram and trying to do this here's this link... https://www.the12volt.com/relays/page5.asp#drto

I just need a little bit of help.  The Radio's accessory wire corresponds with what wire on my stereo Would that be my power wire (red) on my stereo.  If not exactly which wire.  Where it has "fused 12v+"  Do I wire it to a fuse or do I use it as a power wire like using my constant power wire (yellow).  If you could explain that to me I would greatly appreciate it.