you get it from a kid in nimbasa and just tech it to a strong Pokemon
make one of your pokemon learn the hm strength
pekachewww
currently no pokemon can learn ice burn in black or white. how ever it will be the signature move of white kyurem in pokemon white 2
any pokemon that can learn strength can push aside a big boulder
one of you Pokemon in your party need to learn strength.
Wailord and cloyster
u can get strength in nimbasas city in th house beside Pokemon center
auduno
blitzle... i think
raticate can learn both and can be found in many places or evolved from rattata
its hm
Any electric type pokemon.