Some ideas specifically for hynagogic imagery, with the idea of becoming immersed:

Become aware of your peripheral vision. Focus on the scene as it develops in the center of your vision, but also try to spread the imagery out to the edges. Use the cues in your peripheral vision to give the scene a three-dimensional presence. Even if it is just black, you might wonder: are those just shadows? Just as you would in a dark room, relax your eyes and let them adjust. A little patience and then the detail will start to appear.

Look for light, space and time cues. Look carefully at the imagery and try to pick up cues that would help you judge the environment around you. From which direction is the light coming from? Is it sunlight? A lamp? And can you sense what kind of space you are in? Outdoors? Indoors? A home? An office building? Can you guess if it is day or night? Morning or noon? Is it cloudy or clear?

Communicate telepathically. Without moving or straining, try to interact with people or objects in the scene through pure will. Ask them to come closer. Or say hello. Look for some action or acknowledgement that you have become a part of the scene rather than just an observer.

Look around and interact. This builds on all of the above. If you can get a sense of being in a three-dimensional space, direct your curiosity left, right, up and down. Again, without moving your real body. You are instead asking the scene to show you what's around, like controlling a remote camera. Once you can move the view around at will or bring something close enough to touch, then you can be more confident you have transitioned into the dream.