I am turning 21 and i am just suspecting i have lazy eye (left eye) for the past 10 years w/o knowing. how should i train myself to use both eyes tgt?

Eye check: have your eyes tested.you could be blocking vision in one eye! generally patching and retraining your eyes should be done during child hood , at the present time they may try special lenses .or surgery to correct the lazy eye

You can't: Amblyopia or "lazy eye" occurs when the brain decides to turn off the input of an eye that presents a different,weaker or out of alignment image. If caught early and the distortion corrected, vision can be retained.After many years,surgery might help with poor alignment, but the vision cannot be turned back on after the brain left it off for too long.