If you'd like to share the photos you've already uploaded to Instagram to another service (such as Facebook or Twitter), just follow these steps:

1. Tap the Profile tab, then Your photos.
   
2. Tap the "..." link at the bottom right of the photo you'd like to share, then "Share post".
   
3. Tap the green "Share" button next to the service you'd like to share your photo on.
   

If the green "Share" button doesn't appear, you haven't yet connected to the service.

To do so:

1. Tap "Setup sharing", then "configure" next to the service you'd like to connect to (Facebook, Twitter, etc.).
   
2. Enter your login info to connect to the service.
3. After you've connected, tap "Back" and then the green "Share" button next to the service you'd like to share your photo on.