Every game in Roblox is made via the Create tab and comes with a free-to-use app called Roblox Studio. From there, you can use the app to make whatever you want.

To craft the Shark Tooth Necklace in this Roblox title, you must interact with an NPC called the Shark Hunter who can be found in Tiki Outpost (a level 2450 island located in the Third Sea).