Visualization is not an ability every one has. Many people have to learn how to visualize, and not all can do it very well.
What you can do is start small and work your way up. For example: take a marble and stare at it. Take each in each detail of the marble. Just study it for a time. Close your eyes and focus on the marble. Start with trying to visualize the shape. When are able to do this a few times successfully, add more detail. Colour. Then shades and highlights. Gradually add more detail until you can visualize the marble clearly.
It takes time and practice to get done. Try not to get frustrated. Remain calm for frustration could likely hinder you from reaching the goal.
You could also go into other additives. Cleansing and aligning your chakras. Many would say "oh, just open your third eye." No. Work on all and not the one. You could also try meditating with a crystal that helps with imagination and other means of such mental task before and/or during your practice in visualization.
Good luck in your efforts.