Install midnight commander / or cute explorer on the n900 their pretty easy to use. their just basic file explorers but will let you see the folders that a normaly hidden to you (if you start in root).

or just put file in n900 internal memory. (in the root folder of the drive) then go into terminal and type 'root' then enter, then type 'cp /home/user/MyDocs/transitions.ini /usr/share/hildon-desktop/' and thats it
the terminal is case sensitive so make sure the MyDocs hase a capital M and D.

hope this helps

P.S stop PMing me, just post in forum so everybody can read and learn (not that I mind, PM if you need).