How can you get a ferleaf on Pokemon battle arena?

You can't get a Ferleaf in Pokemon Battle Arena.

Here's why:

* Pokemon Battle Arena is a game mode. It's not a place where you catch or obtain Pokemon.

* Ferleaf is a Pokemon. You would obtain it in the main Pokemon games by finding or evolving a specific Pokemon.

To get a Ferleaf, you would need to play a main series Pokemon game like Pokemon Sword and Shield, Pokemon Brilliant Diamond & Shining Pearl, etc.

Let me know if you have any other questions about Pokemon!