This I always do with my eyes open. The idea is like with open eyes I see the light around me. Now, it's not really something you observe physically, it's like imagination in your head. But you don't need to see it with your physical eyes for it to really be there and work. If you have ever had any knowledge of martial arts you will know that Ki energy moves at the will of the practitioner. If he focuses on something, the mind generates energy there. So if you visualize around you a white light, you are really putting white cleansing energy there, etc. JoS explains that you can manipulate both internal energy within you and external energy (absorb energy from outside, etc.), but this is not JoS's invention. It is a real thing. Always think of martial arts like Tai Chi that make you absorb energies from outside, like from the Earth itself, etc.
It is perfectly normal to fail at first. I started in 2017 that I could only visualize small sections of white energy (an off-white, not gray, but off-white energy), today I glow with radiant energy, in fact, in other meditations I also spontaneously visualize gold. This is something that is best acquired by insisting and not giving yourself away.