Once we’d gotten on the train, we could settle down and relax for the long journey ahead.
A.Once we boarded on the train and settled down and relaxed for the long journey to come.
B.After getting on the train, we found it difficult to find a good place to sit down and relax for the long journey that followed.
C.After boarding the train, we managed to find out seats and then to relax on the long journey to come.
D.Once upon a time, we got on the train and enjoyed the long trip that followed.