You defeat them by training against wild Pokemon.
Defeat all 16 Gym Leaders in both Kanto and Johto. If you want a more detailed explanation of how to defeat the gym leaders, go to Seribii.net.
the first seven badges are with the gym leaders that you have to defeat
No, you don't. You cannot face the Sinnoh Gym Leaders in HeartGold.
there are 16 gym leaders in all
Well after you defeat 15 gym leaders in Pokemon HeartGold / SoulSilver go to Cinnabar Island and talk to Blue.
Go to serebii.net and click on heartgold/soulsilver. click on gym leaders.
16
To find blue defeat all of the gym leaders and then go to cinnabar island blue will be there and will accept your challenge if you have defeated all of the gym leaders. Then go to viridian city gym and get through all of the trainers. After this you can also battle red.
i only know two:Chuck and Jasmine go to google to find the other gym leaders
You need to defeat the other Kanto gym leaders. If you have defeated the other 6 except for Blue, go to Cinnabar Island and talk to him there.
Beat the rest of the gym leaders first.
Im sorry..............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................but no