first, you must make many quests and a messenger near the konoha gate will appear ask him
and go to tsunade... then you must go to orochimaru's hideout and head to the big door
which is in the first phase of orochimaru's hideout naruto will say something... after
that head back to konoha (note: for easy going you will buy scrolls)
then talk to tsunade... then you could begin to play as Sasuke in RPG mode.. then go back
to orochimaru's hideout... enter the big room... (The one you went before not the one
where you faced sasuke) then clear the stage and tsunade will give you a reward named
sasuke's kunai.... if you have trouble finding it... it has the +2 to all stats. equip it
to naruto and now you can play as sasuke in RPG mode.. (each time you battle naruto is
replaced with sasuke) then go back to orochimaru's hide out and the clones will be there

If i'm mistaken visit www.neoseeker.com

they got a walkthrough