You can try completing certain quests or participating in specific events related to it. Sometimes, rare drops from monsters might also give you a chance to obtain it.
One good order could be starting with the Tutorial Island quests as they introduce the basic mechanics. Then move on to the Lumbridge quests which are relatively easy and build a foundation. After that, quests like the Vampire Slayer quest can be a good next step as it has an interesting story and unlocks some useful items and areas.
One possible plot twist could be that Naruto discovers he has a natural affinity for a special type of metal that is only found in a hidden realm. This metal has unique properties that can enhance his ninja tools in unexpected ways. Another could be that the smithing skills he learns are actually part of an ancient prophecy. It was foretold that a ninja with Naruto's spirit would master smithing to create a weapon that could save the ninja world from a great threat that is yet to come.