I would like to buy a ticket from Emirates airline online. As I go through steps of booking a flight on their website, it does not ask me to choose the seat and I wonder if there is such an option for Emirates airlines. I remember another airline which did have the step of choosing flight seat.
Yes and no. You book your ticket first then choose your seat:
You can reserve seats through our Manage a Booking page. After entering your Emirates booking reference, you will be able to select your preferred seating option(s). Please note that while every effort is made to satisfy seating requests, these are not guaranteed and could be changed without notice due to unexpected changes in aircraft, or due to operational requirements.