To message other OneMessage users you will need to know their Screen Name. Then open the OneMessage app -> tap the Message button -> then tap the + button in the lower right -> Enter the persons Screen Name in the field at the top of the screen then type you message in the message field. When you are done tap the send icon to queue your message for sending. When you are ready to send your messages tap the Connect button from the OneMessage home screen or icon in the lower of your screen to open the Connect screen. Verify the Connection Method is correct and then tap the Connect button. If you are using your cellular data or other Wi-Fi network then you will use the Network connection setting.