The Messages tab on your Mobile Text Alerts app allows you to view messages you have sent (as well as replies you have received back), and it allows you to send new messages:
Clicking on one of the message threads will show you a history of all messages sent to those recipients as well as replies they sent back. You can also send another message to that subscriber or group of subscribers by typing something in and tapping the "paper airplane" icon.
Sending a message
Click on the "paper airplane" icon toward the bottom right corner to start a new message:
You'll first select whether you want your message to be sent immediately or at a later time. If you select to send it later, it will ask you what date and time you would like to send it.
Next you'll select who you want your message to be sent to; you can select specific individuals, specific groups, or "all subscribers."
After you confirm the recipients, you can type out and send/schedule your message:
Images, Names, Links, and Templates
If you'd like to include an image in your message, you can select the MMS option, and then you'll be able to select an image from your device (or take a photo with your camera). This option also increases your maximum character count to 1550 instead of 160. (Note that each MMS counts as 3 message credits per recipient instead of 1):
Whether you are sending as SMS or MMS, you can select the "+" icon to reveal "Names" and "Link" options:
Selecting the "Names" option will allow you to input your subscribers' individual names into your message.
Selecting the "Link" option will allow you to shorten a link to make it more conducive to a text message. This will also make the link trackable from your "Report->Link Tracking Report" in your web control panel.
Lastly, selecting the icon on the top right corner of the "Content" box will allow you to save the text you've typed in as a template to use for future, or to insert an already-existing template into your current message: