From what age should we start to potty train the child?

My child has completed his one year. Can I start to potty train him now itself?

Definitely why not. Babies are very understanding, they learn whatever you teach them specially in early age. Just you have make a exact time schedule and they will learn to follow it. For detailed information check this http://www.babynology.com/parenting-advice/potty_training_for_your_baby.html

It doesn't really matter how old he is. If he's to the level of understanding it then yes, if not then you should try to force him to understand something he doesn't just because of his age.