To book a ticket on IRCTC.co.in, you must first create an account with your basic contact details. You then enter your source and destination stations, journey date, and ticket type. This brings up available train options, where you select the train, class, and journey date before providing your personal details and making payment by internet banking, debit/credit card. Upon successful payment, you will receive a PNR number confirming your ticket booking. The document outlines the step-by-step process for booking rail tickets online through the Indian Railways booking website IRCTC.co.in.