You can use goCash (and goCashPlus) to book tickets through Goibibo website and Mobile app.
In order to use goCash, you need to log in to your Goibibo account. While booking the ticket, you have to choose goCash as option to pay. You can pay the amount using goCash or through credit card/debit card/net banking.
Please note that goCash gets deducted prior to goCashPlus during payment of your bookings.