Preethi,
P diffusion guard ring means the ring with active layer, p+ diffusion layer, metal1 and contacts i.e basically its a P+ substrate pick up in the form of ring.
You can get diffusion rings by using create--> multipath part or create--> guard rings in the cadence virtuoso/icfb. Press F3 and change the type of ring that you want to create.
There is no particular kind of guard ring layer in LSW that can be used as far as my experience goes so far for 3 yrs.
Note: when you create multipath part ( multiple paths will come together when you draw once i.e diffusion,met1 with contacts,active layers) you can also create your own path with double contacts for the ring or wider guard ring or guard ring with some other layer with it etc.