You can connect your Facebook account to your Photobox account via "My preferences", by clicking "Connect" below "Facebook account connection". This will make it possible for you to log in to your PhotoBox account with the same log in details that you use when logging in to Facebook.
To share your Photobox photos on Facebook, you will however need to share your album. You can read more about how to do this here.
You can also choose to upload your Facebook photos to your Photobox account by clicking on "Upload" in the top right corner of our home page.