In Poser you don't parent clothes, you conform it. There is a Parent button on the tab because technically you CAN parent it (dynamic clothes are usually parented before thesimulation is run, for instance) but in Poser, simply select the dress and click Conform To... Then select the SP3 character (probably called Figure 1 if you loaded her first) And then the clothes WILL snap into place and follow when you pose her. And as EnglishBob said: The jagged feet is probably due to IK. Turn iit off and see if it helps. (Figure -> Use Inverse Kinematics then remove the two checkmarks at Right and left leg)

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You just can't put the words "Poserites" and "happy" in the same sentence - didn't you know that? LaurieA
  Using Poser since 2002. Currently at Version 11.1 - Win 10.