Creating a Distribution List/Group:
Open Outlook 2013
Click on "People" on the bottom left part of the screen
Click "New Contact Group" on the toolbar on the top left
Enter the name of the group you wish to create in the "Name" field
To add members to the group click "Add Members" from the top toolbar
After clicking on "Add Members" you will be asked what method you wish to enter those group members: from outlook contacts, from address book, or from adding a new email contact.
Once you have added the members to the group click "Save & Close" from the taskbar on the top of the page
Creating a New Message to Send Distribution List:
Click on "People" on the bottom left part of the screen
Click "Email" at the top left on the taskbar
In the "To:" field type the name of the Distribution List, Outlook will find the group for you:
Click "Send" and Outlook will send the email to the all the members of the group.
Modifying a Distribution List:
Go to "People" at the bottom left of the page
Find the group in the list and double click
To add a member to the list: click on the "Add-Members" icon on the taskbar.
To remove a member of the list: highlight the user's display name and email address and click remove member from the top taskbar