Ric 4003 Loose Bridge Saddle

I have a 2010 4003.

Got a problem with one of the bridge saddles - A string - noticed the other day a clicking noise, and under investigation it's really loose and vibrating!

Any idea how I tighten this up?

There's a few screws down there, and I don't want to dive in and tamper with the wrong one!

Any idea which screw, and do I need a specialist tool? Can I do this as novice?

Any help please!