I live in the town of Paisley, which is where your granma was born. If you follow the red line, you will find how I got to the Isle of Barra by train, and by boat.
I took my bike on to a train, and got a train to the city of Glasgow. That's the biggest city in scotland, but it's not as big as Chicago.
Then I got on another train to the town of Oban, where I pushed my bike off the train, and waited for the ferry that would take me to the island.