Go to CRM > View Vendors.
Select the Vendor.
Make sure that Vendor has a Mobile Phone Number.
Go to the SMS tab.
While composing a message, you will see a character counter to indicate the length of the message and how many messages will count against your license.
For Vendors owned by an Account, messages will be sent from that Account's available SMS numbers.
For Vendors owned by an Office or your Brokerage, messages will be sent from your own available SMS numbers.
The To numbers will be any of the Vendor's mobile numbers which are recognized as valid.
Non-managers will only be able to see their direct correspondence with a Vendor.
Managers can see all messages sent to and from the Vendor.