The Quality Tab can be used to automatically reject bad data. For example, you can set Intensity to a minimum value; if the intensity of stars in the image falls below that value the image is automatically rejected. This can be useful for automatically rejecting cloudy images. You can manually turn on/off images using the check box in the tree view. Other options include FWHM, Roundess, and Contrast.
Once you have set up some quality criteria, click Measure All. All images will be measured and the ones that do not meet the criteria will be automatically rejected. You can now adjust the Threshold and watch the images tag and untag. You can also export all of the quality measurements to a text file using the Export All button.