Cookie Clicker 3DS is a replica of the original cookie clicker.
You can press the X button to get cookies. Once you gain enough cookies, you can purchase a building. Buildings slowly gain cookies over time. Your goal is to get as many cookies as possible. Once you get a ton of cookies, you can buy upgrades. Upgrades make your buildings more efficient
If you are running a version below 1.7.0, you will have to create a directory. If you installed this game through the 3DS playkit, you can just run the executable. Make sure /3ds/data/CookieClicker/ exists, or on earlier versions it will crash. On 1.7.0 the directories will be created automatically.
Your save is stored in /3ds/data/CookieCollector/user.txt/. Save user.txt to a safe place to back it up. Once you have backed it up, you can either manually remove it, or reset the save in-game. To restore your save, simply place the old one back where it was.
To update CC3DS, you will simply need to replace the 3DSX with the newest version. Or install a newer CIA file.