Take a simple object from your surroundings. Hold it in your hands. Examine it closely taking in every piece of information that it has to offer you. Do not forget about your other senses.
Now put down the object and close your eyes. Try to picture it in your mind’s eye, just exactly as it was when you were looking at It. If it begins to fade, repeat the process.
Now put the object out of sight and write or speak a detailed description of it. Know that without visualisation of the object, you would not be able to describe it.
Alternatively, put the object out of sight and take a pencil and paper. Begin to recall the object and draw it exactly as it appears to you in your mind’s eye. The quality of your artwork is not important here. Just know that object is out of sight and so the image that you produced came only from your visualisation.

Now try the above exercise with a more detailed image such as a photograph or several different objects. Remember to use your mind’s eye to create a detailed description or image rather than verbally recalling what was there.

Now create a mental image of a simple object without a visual reference. For example: an apple. It is easy to remember what an apple looks like, but you cannot describe your particular apple without visualisation.
You can also draw your apple.