So if you're going to download anything to your Tamagotchi ON, you need the MyMeets program:
https://tamatown.com/downloads/ It only works on Windows, and you either need to have Bluetooth LE on your computer already, or you can get a dongle for that. If your computer has Bluetooth but it isn't Bluetooth LE, you will need to go into your computer's settings to disable the native Bluetooth on your computer and then use a dongle.
The MyMeets app works by pretending it's the phone app. You use it to send your tamagotchi a present (with gotchipoints too if you'd like), or you can use it for marriage to a tama of your creation. Your tamagotchi thinks it's either getting a present from the app, or that your tama has gone into the app and married someone there. The MyMeets program doesn't appear to cause any problems, it works very well. It comes preloaded with many new backgrounds, toys, and food to send to your tamagotchi, or there are more you can download from the same website, or you can find more for sale or for free on the internet. Adding items/etc. to the program that you got from somewhere else is very easy. You can also even make your own things to send to your tamagotchi using a different program included with the MyMeets download! Since every toy/etc. is made using specific parameters, there's not much danger of getting one that causes any problems with your tamagotchi (the item/background might not work correctly, especially if you made it yourself lol, but that's it's own problem that will not affect the rest of the device).
You can also use the program to add new games and destinations to your tamagotchi. The ones included with the app are the ones Bandai released in Japan and work fine in my experience. I don't know about other games or destinations that other people have made, I would read the reviews on those kinds of things before trying.
