This feature allows you to change the center of the image. In SAXS mode this is the position where the direct beam would have hit if there were no beamstop, and it is indicated by an X on the false color image. In WAXS mode it is the position where the beam would hit if Detector 2Theta were zero, and it is indicated by an arrow pointing in the direction of increasing 2theta. For a detector with N x N pixels, the X-Center and Y-Center values are often somewhere close to (N/2, N/2), although sometimes data are taken in a mode where the beam zero is close to the edge of the detector, and sometimes the beam zero is completely off the detector. To start recentering, click on "Enable Center Change" (nothing will happen until you do this). The X-Center and Y-Center boxes in the right should change from italic to roman font. At this point, you can change the center either by retyping the desired values in the two boxes, or by dragging the X in the image to the new position.
Very important: you must click the "Disable Center Change" button when you are done. Otherwise, mouse clicks to center may still be enabled and you may get confusing results in other parts of the program.
The windows will change back to italic when you have done this, and the image will be recalculated so that the center of the diffraction pattern is at the center of the image (depending on the Zoom option you have chosen).