In the case of Spirit, Jung does not talk about an individual’s process of integrating archetypal contents as psychological functions: he claims that such a process happened as an overarching development in the history of the human species. That, of course, is a variation on an origin myth: a phantasy, projected backwards into history.
Spirit, the archetype of spirit a pre-existent meaning in the midst of chaotic life, has been morphed, over the course of centuries of human history, from of a separated form of being into an integrated function of human consciousness. But precisely how does Jung think such an “integration” might have worked?
Synchronicities are something that "appears” in an individual person’s life, usually at some particular stage or around some event. Therefore, we can assume that there are certain patterns in people’s lives when archetypes are triggered, resulting in greater likelyhood of experiencing synchronicities.