The Send a Text Message action allows you to send a text message to a contact. The action can be triggered as the first action after a contact enters the Journey's funnel, or as the result of another action. See Fig 1 below. 

Fig 1

NOTE: SMS Messaging (sending "Campaign"-type messages) is still in early-adoption status, thus will be accessible to select customers to use in test-only mode. ALL SMS campaign messages must first be approved by Pinpointe Admin to ensure the contents of said messages do not violate our SMS partner content rules. Please contact Pinpointe Support with any questions.

As with email campaigns, you must first create an SMS message before it may be used in a Journey. To add an SMS campaign text message to a Journey, click the Send a Text Message action node once you have added it to the Journey work area. Doing so will bring up this popup ("Properties") on the right-hand side of the screen (See Fig 2):  

Fig 2

Clicking into the field, "Message", just below the "Send a Text Message" label, will bring bring up a list of all approved SMS campaign-type text messages. See Fig 3 below for an example.

Fig 3

Click on the message to be included in the Journey. Once the text message has been selected, the content of the message will appear below in the "Content" field. See Fig 4 below.

Fig 4

Once you have finished with the SMS setup, click the "Save Properties" button.