Choosing the "FROM" number for a message is done in the Messages tab when you compose a new message.
Finding the Messages section
Log in to PastorsLine and go to Messages (the chat icon, gold arrow below).
The screen will refresh. Click on the relevant group or the relevant contact from the inbox that you would like to message (or create a new message for that group or contact by clicking the New message icon with a "+" next to it).
You can also search for a person or group using the search icon, or find them in the "Contacts tab" or "Groups" tab on the left menu.
Working with the shared, high-throughput, verified toll-free number
Verify that this is the contact you wish to send a message to.
Then look towards the bottom of the screen.
Click on the phone number to open a pop-up menu of number choices (brown arrow in image).
Toggle on the high-throughput number choice (brown box, #1 below). It will turn purple.
Click on the X to save your changes (gold arrow, #2 above).