座席指定列車で

Please take the seat assigned on your reservation ticket.

Your seat assignment is on your reservation ticket. Please take that seat.

Your seat is assigned on your reservation ticket. Please take that seat.

日本人が間違いやすい発音として、seat [síːt] があります。sheet [ʃíːt] のように言ってしまいがちなので、ご注意ください。