adding graphite on floyd rose?

hi..just wanna ask you..when do i must put graphite on the nut and the bridge? n what for ?is it really necessary?

since my guitar has a floyd rose system,how( n where) should i put the graphite ? i've heard that it must be put into the nut and the floyd rose bridge saddles..but which part of the nut and the bridge exactly?
thx u..

note: if you have some photo or picture about it,please(if you don't mine,of course) attached it also in this thread...thx u very much.. :)