You start with sensing their presence, and with that do energy cultivation exercises, then when you start seeing flashed or shadows out of the corners of your eye - but when you look there’s nothing there. And then you start catching the movement and can watch it, and it looks like air or shadow moving, kind of like a cloaked ship in sci-fi distorts light.
I don’t get more than that, but after that I’m expecting it develops to seeing that form get more and more clear and distinct.
And the reason you won’t think you’re hallucinating is because the first thing you did was develop the sense of presence - if the image has no presence it’s fake and an hallucination, but if you can feel it, and by this stage you can feel it’s emotions, then it’s like seeing any animal or person - they’re not just there visibly, it’s there for all your senses especially the subtle ones.
Everybody can sense presence. To develop your recognition of it, and make it stronger do this coffee shop exercise:
Go to a cafe, and people watch. Notice the ambience of the cafe, and how it changes with the people and their emotions. Then don’t look at the people, feel them first. See how the whole cafe feels different if someone walks in who is angry, or laughing, or stressed. And how it lightened up of feels quiet or darker or whatever when they leave.
All that you can feel, even though you’re not looking, applies to beings that have no bodies to see. Its the exact same thing. We just rely so hard on our eyes it kind of downs out the rest, but a bit of practice these rusty skills can be brought up pretty quickly. .