As soon you have the Facebook app installed/enabled (signed-in) on your device you will see the facebook option for sharing under "Share"
This applies to e.g. Twitter, Picasa as well.
1. Choose the Share button within the PS Touch organizer – see attrached screenshot 1
2. Choose e.g. jpeg as file type and touch (select) the project you want to share – see attrached screenshot 2
3. from the upcoming dialog you can choose Facebook, Twitter, Dropbox etc - see attrached screenshot 3
Hope that helps.