In order to send a mass text message you first have to go to the "Automations" page and select the "Schedule Messages" section.
Select what tags to target. Decide on a specific time for the message to go out. And finally, select a specific text to be sent out.
You are also able to use previously created templated by clicking the "Use a template" button under the "Body" section.
You should now be able to set up and send your first text message blast.
Let us know if you have any questions or concerns, we are always happy to help!