Imagine. Start from the imagination. What is happening is you get flashes of images and tend to call that your imagination. Start describing those and the more you describe them, the clearer the images become.
There are a number of way your imagined images can appear in the mind. Someone described it like looking through a foggy window with ice crusted edges. A dark curtain that you are looking through or a sense I am thinking of. Whatever thoughts you get really stem from images so follow them.
Just for the record... if you can imagine the image you are in a 'sense' seeing it with the minds eye not the physical eyes as you are accustomed to. Many of us react to the images that flash past so quickly that we don't think we 'saw' anything, yet we can name what we 'imagined' in our minds eye. That's why we tend to think we cannot visualise when in fact we are doing it at lightning speed.
If you describe out loud what you imagine to be there you will start noticing more and more details in your images.
Consider this; in order to name or label something the mind must see an image of it.
Some will tell you they can see the picture in their mind clear as day, when you meet such a person, that would be the person to do a borrowed genius on. Since describing and teaching someone else what we are doing with our minds is a bit of a challenge