About like this:
In my head, and in my experience, I don't expect the safeguard to slip unless I'm really pulling that handle... but in my wife's head, I'm dangling from dental floss and a clothespin. So to reassure both of us, I pass the slack end of my rope through my carabiner and make a loop, then pass more slack through that loop and cinch it down on the spine side of the carabiner, then tie an overhand _above_ the safeguard.
I don't think it's "really" necessary, but then even if the safeguard somehow exploded and came off the rope entirely, my backup is still through the carabiner and I don't go anywhere. In that case, I'd _probably_ still have a platform or stick to stand on and take some weight off the rope, and I have a backup ATC and hollowblock in my bag I can use to get down... but that's mostly to reassure my wife. Have tried it once or twice for giggles, do not want to ever do it.
