In a nutshell, this is what you do to convert the pose from one figure to another using PoseWriter.  Load the posted donor figure into your scene along with the new target figure you want the pose applied to.  Make sure that the body parts between the figures are the same, otherwise, you will get either bizarre results or none at all.  DAZ Generation 2, 3, and 4 should not be an issue.  IK must be off or, again, you will get weird results.  

                                                                                          

Where 'Pose' appears, that is an entry field for the name of a pose.  If you are actually writing a new pose to disk, that is where you name the pose.  The window below that are the body parts of the figure, double-clicking that window will select all the body parts including body morphs,  Again, the body parts must match or the pose won't translate.  Right-click the window for the contextual menu and select 'Copy Pose' from the Donor.  Select the Target figure, right-click, and select 'Paste Pose'.  If everything goes well you will get the pose transferred between figures.  Below is a preview of a V4 WM pose transferred to the V3 WM 17k figure.  Not an exact match but close enough to tweak.