Single product in Subscription Groups

Hi iPhone Developper,

This is Hayto from Tokyo, Japan. I am looking for how to make product without levels into subscription groups.

As I am quoting as follows, I found the document which refers that we can make single product. But I can not find how we can set single product without levels into subscription groups or products with same levels.

All subscriptions must be part of a group, however you are not required to differentiate them into levels. For example, you can choose to offer a single subscription in-app purchase, or you can choose to offer multiple subscriptions and assign them all to the same level within the group.

URL which I quoted is as follows.

https://developer.apple.com/library/content/documentation/LanguagesUtilities/Conceptual/iTunesConnectInAppPurchase_Guide/Chapters/CreatingInAppPurchaseProducts.html#//apple_ref/doc/uid/TP40013727-CH3-SW10

Could you kindly tell me how to make subscription product into subscription groups and how to make multiple products with same level into a group?

Thanks,

Hayato