Reserved SignalProbe Pins

This has got to be a stupid question, but I just can't figure it out. So I've used the Pin Planner to reserve a few named pins as SignalProbe outputs. They're named TP20-TP23, after the labeled testpoints on the PCB that they connect to. TP20 is, for instance located at PIN_AA3.

How do I actually connect up signals to them using SignalProbe? When I try going through the dialog box, it tells me it can't add a probe there.