To define the local coordinate system (LCS) of one of the objects in your subject file, the object should already have a surface file specified for it. This file, whose vertices are expressed in the object's CT reference frame, was probably created by Surface3D or a third-party application. Before tracking an object in X4D or Locate3D, you should define an LCS for it because the tracking output for each X-ray frame is the transform from the X-ray lab frame to the object's LCS.
Follow these steps for defining an LCS: