This is very simple.
To send a new message from inside the app:
Tap the new message button at the bottom right on the home screen.
Type in the contact number, or add a contact from your phone contacts list by tapping the Contacts icon on the top right of the new message screen.
Just like any messaging app, type your message text, or select an image to send.
To reply to a message from inside the app:
On the Messages screen, you will find a list of the sender(s).
Tap on a sender to whom you want to reply.
Just like any messaging app, type your message text, or select an image to send.
To receive a message from inside the app:
You don’t need to do any additional provision once you have the app with a number ready.
When a new message is received, it will display on the Messages screen.
Additionally, if the app is not open or your screen is locked, you will get a notification on receiving a new message.