Hi NPTech,
Do you have Office 365 after the service upgrade? If you are not sure if you have Office 365 after the service upgrade, here’s how to tell whether you’re using Office 365 after the service upgrade or Office 365 pre-upgrade: the different colors, navigation, and URLs for Help content:
http://office.microsoft.com/en-us/am-i-using-office-365-after-the-service-upgrade-HA103982331.aspx?redir=0
I suggest you refer to the steps via these two threads you mentioned.
After you finish the steps, please refer to the following steps to login to the Exchange admin center to set the External Contacts.
1. Login to the Office 365 Admin Center with the account you give the permission.
2. Select the Outlook button on the top.
3. Change the URL from https://xxx.outlook.com/owa to https://xxx.outlook.com/ecp
Thanks,
Jason Jiang