How do you get to the gym in Fortree village?

Proceed to Route 120 and get the Devon Scope from Steven, then return and the hidden Kecleon at the Gym will flee.

Head towards route 120, when you come to a bridge, Steven will appear. He talks about the Pokemon blocking the path, then gives you the item to clear this Pokemon. Now go back to the gym and use the item on the Pokemon blocking the way.

Go to the route on the right of Fortree village and when you reach the bridge,a guy called Steven will be blocking your way.Talk to him and he will let you battle a Kelceon.Win or catch it then Steven will give you something use that thing to kill/catch the Keleceon that is blocking your way to the Fortree Gym entrance.

You need to go past that city and steven will give you the right thing for it

Go up the road and talk to Steven and he will give you the Devon Scope and then you can go in the gym.

Omg man this is easy keep walking right out of the city and then if you don't see steven there head down and follow the path until you see a bridge and steven will be on the bridge and he will give you somehting that will let you get thourgh (thurs and invisible pokemon)

Go to Route 120, go to a bridge, then there you will find Steven. He will show you a Pokemon using a telescope. Catch it or defeat it, then Steven will give you a scope thing, then go back to the gym and use it on the invisible pokemon.