Once you login as admin, http://localhost:8080/share/page/user/admin/dashboard you can find customize dashboard button on right top corner(ver 4.0) or a setting symblo(5.0 onwards). Once you click that you can change the layout or select the dashlets of you choice.
thx for your reply for that I already knew but I want every user to have the same default dashboard when logging but the default I want instead of the default alfresco but I want