Yes, you put in the safety first, then the spring and plungers then the extractor. Note that the plungers are not the same, so make sure the pointed one goes toward the rear and the one with a flat side goes to the front. The flat goes inward to hold the extractor in.
You compress the extractor spring by using a thin screwdriver or the extractor itself to press back the spring plunger. If needed, a wood dowel can be used to push the extractor. It's a bit tricky and best done inside a paper bag (no, I am not kidding) but pretty easy once done a few times.
Jim