In LCLS-I, given experiment and run, e.g. mfxx1005021 run 16, look at /reg/d/psdm/mfx/mfxx1005021/calib. Under this one can find the detector type, the detector instance (where in the hutch, which of n cameras), and under that the various sorts of calib information.
To use the calibration information in e.g. python, one can either read the file using numpy.loadtxt() and reshape the resulting array, or one can use psna tools. To do the former, it's simplest to cd to the relevant directory (or carefully point to the path) and do what's in ~philiph/psana/detdaq21/epix10ka/dumpPedRms.py. To do the latter, see e.g. /cds/home/p/philiph/psana/./mfxc00118/cpo/junk.py.
In LCLS-II, ...