When can you use the exp share item in emerald it says Dad.. theres a time and place for everything u'll know when its right or somthing like that can anyone help?

In Pokémon Emerald, you can use the Exp. Share item after you receive it from an NPC in the Devon Corporation building in Rustboro City. Once you have it, you can equip it to a Pokémon in your party to share experience points with other Pokémon that did not battle. The message you mentioned refers to the narrative context in the game, indicating that you may need to progress further in the story to access certain features.