What's required to assign a phone number to a conference room phone?

[Mike Boehm]

Howdy,

We have purchased some Yealink CP960 phones to go in our conference rooms.  Based on the information on this page:

https://docs.microsoft.com/en-us/microsoftteams/room-systems/skype-room-systems-v2

I have assigned the Conference Room account the "Meeting Room" license which shows that it comes with:
S4B Online Plan 2

Phone System

Microsoft Teams

Microsoft Intune

Audio Conferencing

We need our conference phones to be able to make phone calls  if we need to dial into a meeting somewhere but I can't seem to assign a phone number to the account.  It doesn't show up under the Voice Users in the Admin Center.

Do I need to assign it an additional license to activate it as a Voice User or what is the best way to get this to work?

Thanks!

[#2]

@Mike Boehm 

Do you have calling plans, or do you use Direct Routing? 
I always recommend Jeff's post on the subject. This article takes you through the process: https://blog.schertz.name/2019/02/creating-microsoft-teams-rooms-accounts/  

[#3]

@Mike Boehm yes you need calling plans or direct routing to assign a number and to place calls from the room.