Go to the library top floor
You can't you just have to beat him and get it
Hearthome's badge
in the 1st gym badge
you get the coal badge after defeating Roark in eterna city
if you are looking for the third gym badge i suggest Veilstone city.
Get the first gym badge
You can use the GTS in Pokemon Platinum after you get the first gym badge from the Oreburgh City gym.
The fifth gym leader in Pokemon platinum is crasher wake but you get the fourth badge.
Sorry Pokemon fan I am afraid you cannot but if it is your pokedex, you have wifi, one badge and access to jublife try getting it on the gts
you must beat the eighth gym leader and he will give you the badge.
Once you obtain a badge it's permanently stored in the badge case.
umm...you beat the 7th gym