When you leave the railway station, you will see the viaduct outside, and go up from the overpass on the side, above which is the bus rapid transit system. From there, take the express 1, express 2 and express 3 lines to the terminal, and then go back to the ground. When you get out of the terminal, you will find the bus stop. Get on any bus (if you don't feel at ease, ask if you want to go to the ferry, and the driver has a good attitude) and take a stop and get off the ferry. Or you can walk there, but it's not a five-minute walk, and you can also see the sea view. You can see Gulangyu all the way from here, just be close. The nearest place is the ferry, a very lively square.

When you get there, ask others which entrance is the ferry to Gulangyu, because there are also tourist ferries nearby. Remember, you don't have to buy a ticket after you go in. You only need to buy a ticket in Gulangyu when you come back from Gulangyu. Don't listen to those soliciting, those are tourist boats, more than 100 yuan. Gulangyu Island is opposite the ferry, and it will be on the island in less than ten minutes.

In addition, I recommend you to take the BRT, because there is no traffic jam, and experience it by the way.

Have a nice trip! I am from Xiamen. I am used to taking a bus. I don't remember many roads. I can only tell you this. I believe it's easy to find. BRT has ambiguous platforms and service personnel. You can ask.