How to add storage on my iPhone 4s?

How do I add storage on my iPhone 4s?

Added (1). I can't add any more apps or music on my phone.

You can't get more storage space without deleting stuff. If its full, its full. Like a box if that's full you can't put more stuff in it without it falling out and you won't be able to put a lid on it. You can't magically make it bigger.

Sync it to your itune download all apps and upload only favorite apps on your phone.other purchased apps will be on you itune for keeping. Just resync it tick those you want to be added back to your phone.movies also you can remove movies that you already watched.

When you buy an iPhone there is an option to what size of storage you want.unlike other phone with customizable storage cards.