You can rig in Poser, in the Setup room. You will need to use the Bone Tool to add “bones” and then use the grouping tool to to assign those “bones” to your mesh. Once you have created your rigging, or bones, and assigned everything, you can go back to the main room (I forget the actual name of the room) and manipulate the rigged mesh.
That is about I know about it for sure. I have only messed with rigging in Poser a couple of times, and only made it work when I imported rigging from an exsisting figure.
If you want to know more about rigging or using something you have modeled inside of Poser, you can check out the forums at the following places:
You will have to set up an account with the main site at all of those places to see or ask questions in their forums, but the sign up is free, and you are not obligated to purchase any of their stuff.