Even though your readers have downloaded and are signed into the Twitter and Facebook app on their iOS device, they are still not able to share articles to these networks from the epaper app. They will not be able to see the Twitter/Facebook logo in the sharing dialogue box:
In order to share articles on Facebook and Twitter, the reader has to sign in through the settings app on their device.
This is how to do it
1. Open the Settings app:
2. Scroll down till you see Twitter and Facebook
3. Press the network(s) you would like to be able to share to
4. Enter your account credentials, and press Sign In:
5. Done. Now you'll see the Facebook and/or Twitter logo in the sharing dialogue box:
It is not necessary to install the Facebook and Twitter apps.