Inputs - salvaged sleeper relics (hulls, defenses, etc), racial datacores, subsystem datacores, hybrid interface (not consumed). The complete list can be found in the relic description. Output - a random subsystem determined by relic type (offensive, defensive, etc) and racial datacores. Or nothing if you fail. You can do reverse engineering only in experimental labs in POSes, or caldari outposts (0.0).

I am sure there are good guides explaining it all in detail, but I can't find any right now.