You need to sign up for Raptr, then use their client to upload trophies to your Raptr account. Then you link the Raptr account to your Gspot account. It will take some hours before your trophies update and are shown here.
Yup, you have to download Raptr's client and update it from there just for the PS3 trophies, and it isn't very good at all. Looking at my profile there's a lot of missing trophies and running the update via the client doesn't seem to do anything.