To view your text messages in the mobile app, click on the Inbox icon from the lower menu.
From the Inbox screen, you have two options:
Personal Inbox
Groups Inbox
Your personal inbox is available directly from the Inbox menu.
To view your Group Inboxes, go to the upper left and click on the menu icon ( ≡ ).
From here you can view the Inbox for the Groups to which you are assigned. (This is related to call flows directed toward Groups) . Click through a group and see the voicemails and text messages for that group.