It's a realm that you create in your mind and can go there when your consciousness is about to fade and your perception of time comes grinding to a halt, making It (perception of time seem) infinite. Whatever state you died in with your idea of heaven in mind is how you will "experience" it. For you, in that ever-narrowing iota of changes (that we all feel as time), your brain is about to enter its final state. All of that DMT which gets ejaculated by your brain and that idea of heaven (or hell) becomes your conscious state for "eternity," like an imprint on your brain. This is where some religions emphasize the right states of mind in life and in death. Your heaven or hell is literally in your head, as your own imaginary construct - like your own personal virtual reality, but "forever" from your perspective.
You want to go heaven? Just imagine it and really delude yourself with the belief of it. Hold on to that belief for the rest of your life, even during the moments of your death. And viola - you're fucking prime cunny and living out whatever other fantasies you have, for as long as the universe is around.