Under the 'Personal Info, Password, and More' tab, you'll find the 'Java Realms Profanity Filter' tab with its relevant toggle. The toggle is on by default, but you can click it to switch between on and off as you wish.
Herobrine does not and has never existed in the game naturally. In order to have Herobrine appear, you will have to download a mod. If you don't know how to find and install mods for Minecraft, wikiHow can help. The most common Herobrine mod is the burner Mod, available on MinecraftMods and in the Minecraft Forum.