In nimbasa city, theres a kid on the 1st floor of one of those buildings on the left side of town that gives it to you.
House above Nimbasa City Pokemon Center
you ment strenght you get in a house behind the pokemon center in nimbassa city ps it is a boy
in Nimbasa city the building on the top left talk to the lady on the left
Strenght is an HM move, teach it to one of your'e pokemon. to use it just select your'e pokemon and select strenght.
To use strenght outside battle you need: A Pokemon that knows strenght or the HM so you can teach it to a Pokemon The Mine Badge from Byron in Canalave City. Have a Pokemon knowing strenght on your team and go to a place where you need strenght. Press A in front of the big, grey boulder you want to move and use strenght. Now when you walk, you'll push the boulder in front of you. You don't have to use strenght for every new boulder, you'll only have to re-use it if you go in another room.
With hm strenght.
look around olovine, there will be a sailor in a restraunt
you aquire it later in the game
Find the warden's gold teeth in the safari zone then give them to him.
Go to Iron Island and talk to Riley, he'll give it to you.
Fly, Surf, Strenght, Waterfall, Cut, Dive.
you need some HMS such as dive strenght and rock smash