Go to Administration, then Settings.
Enter the desired settings within QuickLink Defaults menu and save. This will be applied to all of the first QuickLinks that users on the account create.
Once users change the QuickLink settings, within the realm of their permission set, the Settings of the last QuickLink sent out will be remembered and applied to their next QuickLink (except for Public with Password settings -- users will be prompted to enter a new Password for each new QuickLink).