Where do I find Coupons on BookMyshow?

Coupons can be selected after a successful booking. You can select them using the link shared in your confirmation email. You can also find an option to add coupons under 'Purchase History'.

P.S:  Why don't I see the option to select coupons? 

That's a concern 

To be honest coupon selection depends on the location you book at. Only if the brand outlets tie-ups with the cinema, you get to select one.