This achievement is missable. After obtaining the Life Giver achievement you'll be back in the train. You'll get past a door after seeing Finn messing with a fire extinguisher box. Shortly after, before reaching Finn, there will be a sketch book in one of the train cabins on your right. Pick it up to unlock this achievement
You can unlock this and all the other achievements by following the 100% walkthrough I did for Maka's channel.