Hello. This is Hiro From J-Hoppers Hiroshima.
In Hiroshima,most of sites are accessible from Hiroshima station(south exit) by street car.
But if you travel with Japan Rail Pass, you can use Hiroshima Sightseeing Loop Bus called "Hiroshima meipuru-pu" for free!
get on the bus and when you are ready to get off, just hand it to the driver. They will return it after checking.
If you don't have a Japan Rail Pass,
here's the details about fare!
200 yen/ Adult (12 years or older)/per ride
100 yen/ Child (6-11 years)/per ride
One-day pass400 yen/ Adult
200 yen/ Child
＊You can also use an IC card, "PASPY" / "ICOCA" to pay for the fare.
I think it is very convenient way to transfer from Hiroshima station to city center after you arrived Hiroshima by Shinkansen(Bullet train) from other cities.
Hope it helps you make your trip more enjoyable!!