try to set the value of
\verb| \leftmargin[n] where n is {i,ii,iii,iv,v or vi}. At|
each level, the left margin is indented with the value of
\verb| \leftmargin| unless you
modify the value above.
ex :
\verb|\setlength{\leftmarginii}{2cm}|
%will indent the second level 2cm compared to the
first level.
these declarations must be made outside the list environment. (so in the
preamble if you want this for all your lists).