Same place you get all your thoughts. In your brain.
Spirituality issues forth from the space between what we want to be true and what we don’t know, and is filtered by the appropriately plausible. We don’t know whether there’s a God out there, He’s keeping mum on the matter, but we want there to be one, so we invent ideas about what God could be and pick the nicest sounding, most plausible scenario.
Once this is accomplished, then you can start down the path of what is commonly called prayer, but is more appropriately called mysticism. Sit quietly and commune with your mind and subconscious. Treat whatever random thoughts or feelings arise in the same spirit as improv comedians.
Next time you watch little kids play, pay attention to the conceits that they dream up. “I shot you with my laser gun!” “No, I had a laser shield, you can’t shoot through it!” Normally that’s enough to start a little argument until the kids can agree on the rules of their impromptu game. Or they just get bored of it and do something else like play video games, where the rules are more well-defined.
Improv comedians do the same thing, only without the argument. “I hit you with my laser gun!” “Oh you killed Han! No wait, he’s getting resurrected by Chewie the undead necromancer!” The idea here is Yes And. You take whatever your scene partner declares and make it reality. Then you build on top of it. Improv scenes are spontaneously generated little worlds and stories that follow their own logic.
Spirituality is the same thing. You can use existing religion as a jumping off point or just start with nothing and define the universe. Mysticism makes it real, it’s like doing improv, only with your subconscious mind. Whatever you want to be true, whatever your mind can accept, can be true. That’s spirituality.
When you follow a mystic path long enough, it stops feeling like playtime and starts being real. You’ve primed your mind to actually see through the lens of your new world.
The scope of spirituality is literally any thought that humans can imagine is real. It can be as silly as Pastafari or as serious and scary as Scientology.
I suggest going back to your roots, this is the easiest way to make it all real. If your parents were Christian, start digging into Christianity. Do you like the idea of God? What kind of God would you like? Christians have three, and lots of saints too if praying to God doesn’t float your boat.
This old boy made his own spirituality out of base materials provided by a reclusive and little-known spiritual teacher by the name of David Hawkins. If I had to do it again, I’d have paid more attention to Christianity. But my mystic pathway has already been created and walked down and solidified, (petrified? ossified?) and there’s no changing it now.
The nice thing is, all spiritual thought plays by certain rules, such as Yes And. Turns out humans all want similar things out of “what they want to be true.” And mysticism is easily recognizable once you learn the basics and have done enough of it. So it’s not terribly difficult to take complicated ideas, break them down, and reason about them using “spiritual logic.”