Dear @Manmit , Golden Sunrise,
Yours is a Basic FAQ, what many people have asked from time to time. Books could be written if a learned person write on it. Me ain’t one. So let me opine a little whatever I feel about – Light.
Light is the glacier from which the river of life springs out. It is the source, protector, nurturer, developer, fulfilling and the destiny of life. Always being within, we all come out of it and merge into it. Light is actually the Cosmic Energy which has created the Universe and everything in it – Living or Non-living. An infinitely nano milli-micro part of it has kept You being you and Me being me.
Do not worry, how to become light as we all one day are going to merge in it. Correction in your statement – Saints have not become Light and left their body, They left their body and merged to become Light. Cosmic Energy is often referred to as Light because it is formless yet omni-present. Probably, our ascended masters and Sages, in their Clairvoyance, have felt this brightness and to explain to commoners, have called it Light.
It is the same state, which Lord Krishna has manifested to Arjuna in the conclusive canto of Shrimad Bhagwad Geeta – Formless, Comprehensive and Infinite.
Greatness does not come from being big and mighty…….Small begets Big, it comes from our humility and selflessness. With an ambition to gain powers/supernatural powers will only get us Ego. It will not bring us near to the Light. Forget thyself and you are into it.
Hope I am clear in my opinion.