How do I know if I use photo stream?

You can check to see if you have the photo stream option in Settings>Photos. If you have photo stream, it will show in there. If you don’t have the option, your Apple ID was created in the last 5-6 years. Recently created Apple ID’s no longer included Photo Stream. If you don’t have it, there is nothing you need to do.

If you have the option and it isn’t enabled, you aren’t using it.

You can also check for a Photo Stream album in the photos app. If there is no album there you aren’t using it.