Redmine

I am using Redmine in order to offer a quickview of how many people are online last 2 hours

I just want to add a menuItem to the project_menu,which I foundin "lib\redmine.rb",
first:
I added permissions like "
map.project_module :users do|map|
map.permission :view_users,{:users => [:index , :find_lasts ]}
"
second:
I pushed it into project_menu like "
menu.push :users,{ :controller => "users" , :action =>"index"}
"

third:
I registered the activity in the Activity.map like
"
activity.register :users

"

but I cant find the menuItem I was trying to add.Why?

thanks for help......