Learn how to send an instant message on your iPhone. Tap the Messaging Icon with your finger. To compose a new message, tap the New Text icon in the upper-right hand corner. Enter a phone number or a name from your contact list into the "To:" field. Type in text message using the keyboard at the bottom of the screen. When message is complete, tap Send. To return to message list, tap the Messaging Icon again. To text a reply to a previous conversation, tap on that conversation, add text and tap Send. To send a text to a contact directly, tap the contact and then Text Message. Tap Text Field and enter the text message.