Miyajima is one of the World Heritage site in Japan. It is very popular destination for the tourists.
You can access to Miyajima by Japan Rail Pass with no extra charge. But you have to take a local train and Ferry. I show you some images and explain how to get there.
At Hiroshima station
First of all take Shinkansen to get Hiroshima. After get off Shinkansen at Hiroshima, move to platform 1, Sanyo Line bound for Miyajima-guchi and Iwakuni. You will see the sign for Miyajima. You will find the platform very easily. The local trains are operated every 15 minutes in daytime, 10 minutes in peak time. So if you miss the train, the next train will come shortly.
Please refer Hiroshima station guide to get some more information in the link below:
Take a train to Miyajimaguchi
After arrival at Hiroshima station, change to the local train to get Miyajimaguchi. Miyajima-guchi is 9th station from Hiroshima. Trip time is about 30 minutes.
Catch the ferry to Miyajima
After get off the train at Miyajima-guchi, you will transfer to Ferry. You will see the ferry terminal at the entrance of Miyajima-guchi station. It is only 3 minutes away. We have two ferry services at Miyajima-guchi. You have to take JR Ferry if you use JR Pass, Sanyo Sanin Area Pass, Kansai Hiroshima Area Pass and other JR West Rail Passes.
The ferry service runs every 15 minutes and every 10 minutes in peak season. Usually three boats are operated continuously.
It is very short cruise to Miyajima. It takes only 10 minutes. Big Torii Gate of Itukushima Shrine is usually on your right side.
Miyajima is a small island. You can access the world famous Itsukushia shrine on foot from the ferry terminal.
You can visit both Hiroshima and Miyajima by day trip from Osaka. Please find the link below to find the sample itinerary:
Hope this post will help you build your trip plan to Miyajima.