Underneath the saddle is the mount, with one tightening bolt. Loosen the bolt and tip the saddle up or down, as required. Chances are you should take the whole top of the seat post apart, clean it and look at the serrations of the mount. They might be just fine, or they could need some cleaning up. Once inspected and ensured that all is well, assemble the unit, with the saddle loosely installed. Then set the angle you want and snug the single bolt, on the saddle post top up. Check your tilt and, if satisfied, tighten the assembly enough to ensure that it will not slip or tilt when in use.

Hope that is a help.