How does one go about finding them and becoming a member nowadays, if in fact they’re still active?
Not sure. The idea of a secret society is so over rated. Most of them, whether magick or political based, are just a bunch men who are convinced they have more power than all others and most of them see women as disposable garbage. The types of men that wrote the bible because they hated the idea of women having power and wanted to make sure every future generation saw women as only tools that were meant cook, clean, pop out baby after baby, and serve their husbands. Those are the types of organizations I think of when I hear the word secret societies.
Nah, I’m not into that kind of secret society.
The Gentlemen for Jupiter is an example of the kind of society I was thinking of. Despite the name, the Gentlemen for Jupiter admits women and men, as far as I can tell, and I like their mission to increase prosperity within their communities. Rufus Opus and Jason Miller attribute their membership to unique advantages that fast-tracked their ascent and Great Works.
I’d like to join the Gentlemen of Jupiter if it’s possible. It’ll probably take more than asking, and I don’t know anyone in there, but it couldn’t hurt to put the question out there.
I don’t know anything about the topic, but don’t both of them offer courses? I should think if you took a course and excelled, and showed the right attitude and aptitude, they may be more likely to hook you up. Maybe, anyway. 
Not my thing at all but that’s usually how you impress people in life, by proving through steady actions that you’re someone desirable, who brings a lot to the table, and who they’re missing out by not having - never EVER be a beggar at anyone’s gate!