How do you get on the train on mystery train island?

Before you can start the detective quest, you have to walk through the whole train and speak to all of the passengers and crew. Once you speak to everyone, go to Thomas Edison's cabin to see his...

You go into the luggage room and there is a door at the top now open

Just go to the left, and you'll see a man struglling to push a heavy paggage. Click on him, and your character will ask if the man (Thomas Eddison), needs help, and Thomas will say yes. Build a ramp...

you must do them in order from smallest to biggest

Easy. Once the porter flings the order sheet out of the train, you grab the notebook which is simply right in front of you.