Write an email to the railway booking clerk asking him to reserve a seat for you.

 From       :siddiqurrahman@gmail.com
To            :nazrulislam@yahoo.com
Subject    :For reservation of a seat.

Dear Sir,
I would like to inform you that I will travel to Sylhet on 15 September 2017 by train. May I request you to reserve a first class seat for me from Dhaka to Sylhet on 15 September 2017 at 10.30 train.

Thanking you

Yours faithfully
Siddiqur Rahman