Defeat your rival on the way from Slateport to Mauville city.
when you have got the itemfinder. Click start then click on bag and then press the right button on your +control pad. click on the itemfinder then click use. The itemfinder will detect any items around you that are berried.
Press use to use the itemfinder and if it dings you have found something. Walk in the direction you are facing then use the itemfinder again. continue until the itemfinder starts shaking wildly and press A facing the spot and you will find something.
somewhere
If you have the itemfinder app for the pokech, go by the bottommost building and use the itemfinder.
Just find the itemfinder press A and select 'use' then you're using it!
The itemfinder will point you in the direction of where hidden items are press A in that direction to find the item.
Simply press the A button in the direction the itemfinder is pointing to.
In Pokémon Yellow, you can obtain the Itemfinder by visiting the house in Goldenrod City, which is located north of the Pokémon Center. Inside, you'll find a man who will give you the Itemfinder after you show him that you've caught at least 30 different Pokémon. The Itemfinder helps you locate hidden items on the ground throughout the game.
Pokemon emerald
I'm sorry but itemfinder only finds items not Pokemon wish it would
There are plenty of hidden items you cannot see in the world of hoenn use the itemfinder to seek them out!
You don't need to dig to get an item if the itemfinder responds. All you have to do is follow the signals on the itemfinder until you reach the spot where the item is. Then you press the space in front of you, or next to you and you should pick up the item.