use the admin gatekeeper function to make the groups form viewable only to the admins and the if condition for the left side menu to create groups and viola!

You would need dig the groups views a bit.

I dont understand ! What you mean ?

I am new at elgg (i intalled it yesterday)

The version that i use is 1.8b2

@Z - you'll need to do some **php coding to achieve that ! ;-)

@DhrupDeScoop - I found this http://docs.elgg.org/wiki/Gatekeeper but i dont know php :(

Can you help me, provide me this code ? 

u r guessing ?
not gatekeeper

try :-
    if (isadminloggedin()) ...
if you "don't know php' ;-( 
it's gonna be quite very hard to *code what you want..
but you can always learn ..