Do you know the CIP rules. Cahn-Ingold-Prelog-Rules. You have to figure out the order of the substituentes. Hydrogen has the lowest value.The others according amount and order number in the PSE. The molecule has to be moved in this way that hydrogen is behind. The other 3 Substituents gave according the order 1 2 3 in clockwise R and anticlock the S configuration.
I asume S S R R. If I am right. Somebody can confirm.