Select the "Content" sub-tab, then click "+New Custom Content Set":

The New Custom Content Set menu will appear. Enter values for the required Name and Workstream fields (marked by blue asterisk), then click "Save Changes":

A new window for "Content" will appear. Click "+Add Content" to

Enter a value for the required "Content Name", then select the SMS toggle in the "Channel" field. When finished, click "Next":

The Content Customization menu will appear. Enter the text that you wish to send to recipients in the "SMS Message" field:

If desired, users can also select from a list of variables to include by clicking "+Recipient Information." When finished, click "Next":

Filter conditions can be applied to exclude potential recipients based on various attributes. Use the "Attribute" drop-down menu to select an option, then use And/Or/If menu options to combine with Attribute factors as necessary:

Alternatively, use the "Enable for all applicable" toggle to create the content absent any specified filtering options. When finished, click "Next":

The Review menu will appear, displaying your content as it is currently formulated. To make additional changes, use the "Edit" buttons to re-open the Customize Content menu. When ready, click "Confirm" to save the content as-is:

Your customized content is now saved, and can be used in any applicable campaign.