If you want to edit the vray material in Material Studio (assuming the material has .vismat as extension) you 'Right-click' on Scene Material and select 'add material -> add vraymtl' it will then pop up a browser box where you search for your .vismat material.
If you want to open it in VraySU you open the material editor and once again right click on Scene Material and select 'add material -> add vraymtl'.
Edit: Sorry...it should be right click and import new material'
Hope that helps,
Rob