Alignment on 5 axes

Dear all,

I have some experience on 3 axes done with my CNC mill, but now I would like to jump to 5 axes and I have a doubt about the workpiece alignment.

On 3 axes I decide the origin on my CAM software, then I select the same origin on the workpiece once fixtured on my table and the G-code does its job with the same coordinates. No problems for me...

But on 5 axes, the origin of X and Y is already on the C axis, so how does the probing/zeroing procedure works?

I'm also looking into the process of this operation, hope to receive an answer soon! drift hunters