i use heart gold version
i want to transfer to omega ruby

I think this answer can help you. I found it on another Pokemon forum.

If you are talking about transferring pokemon form 3rd gen to 4th gen you need an original DS or DS lite (the models with a GBA game slot). The GBA pokemon game must be in the slot before the transferring can be done.

You also will need to have beaten the elite 4 and champion, upgraded your pokedex to the national dex, and gotten to the Pal Park in you Gen 4 games. Pal Park is located in Fuschia City in Kanto in HGSS versions and is on the route south of Sandgem town in D/P/Pt version.

The transfer option is on the main menu when you first start the game up. Once you select that option you must select 6 pokemon from any of of you GBA game cartridges boxes. Once you selected the six pokemon select yes to begin transfering.

FYI the pokemon you are transferring can not know HM moves.

To get the pokemon you have to compete in a mini game. Just walk around the fields, or surf on the water until all the pokemon show up. The balls you are given act like master balls so all you need is 1 encounter to catch the transferred pokemon.