The lead notifications are typically distributed to everyone who is an employee of your account and is on the Sales Notifications contact list. To find lists, go to Contacts->Contact Lists, find the list Sales Notifications, and add the employee to the list. It is important, only contacts who are employees will get lead notifications. Hence, there may be the situation where not everyone on the Sales Notifications contact list will get a lead notification (non employees of the account who are on the list will not get notifications)