If you are talking about Defog(HM05), then you will have to beat Crasher Wake first in order to use it outside of battle. It is somewhere in the Great Marsh. In Platinum, it's Fantina, and after you beat her, you can use Surf.
Defog
Let me name: Roark-Rock smash Gardenia-cut Maylene-Fly Crasher Wake-defog Fantina-surf Byron-strength Candice-Rock climb Volkner-waterfall This is my list so you can figure out. Empoleon
fly
u get to use certain HM's once u beat the gym leaders
If you are talking about Defog(HM05), then you will have to beat Crasher Wake first in order to use it outside of battle. It is somewhere in the Great Marsh. In Platinum, it's Fantina, and after you beat her, you can use Surf.
You have to go to pastoria city and defeat the gym leader crasher wake in a poke'mon battle then he would give you the HM surf.
Beat the gym leader Crasher Wake (gym number 5 I believe) and teach the HM "surf" to a aquatic pokemon. Then, simply "talk to the water" to go in it.
You don't receive Surf. I think you find the HM. Anyway, to use Surf, you need to beat Crasher Wake from Pastoria City. <<<<<< what a lie first of all you get it from cynthias grandmother in celestic town and if you beat crasher wake you can use defog not surf :P beat fantina first in hearthome city to use surf
after you defeat crasher wake you go to the celestic town and you give the old charm that cinthya gave you to her grandmother and then go into the celestic ruins and click on the pattern at the back then the grandmother will come and give you HM 06 surf
When you beat Pastoria's Gym Leader Wake, go to the great marsh and speak to the person on the right to get the HM.
first u have beat pastoria's gym leader then wake into the great marsh will find a person on the right he will give you hm 5 (defog)
Defog
Let me name: Roark-Rock smash Gardenia-cut Maylene-Fly Crasher Wake-defog Fantina-surf Byron-strength Candice-Rock climb Volkner-waterfall This is my list so you can figure out. Empoleon
fly
u get to use certain HM's once u beat the gym leaders
hm defog