If you are viewing a message or another label, tap the Back Key until you return to your Inbox.
The icons at the bottom of the screen allow you to navigate within the Gmail Application.
While viewing your Inbox, swipe the screen up and down to scroll through the list and use the following icons:
Compose : Tap this icon to start a new Gmail message.
Search : Tap this icon to search within the Gmail application.
Labels : Tap this icon to view your messages by Gmail label.
Sync : Tap this icon to sync your Google Account(s) on your device.
While viewing a message, swipe the screen left and right to scroll through all of your messages and use the following icons:
Archive : Tap this icon to send the message to your archive folder.
Delete : Tap this icon to delete the message.
Labels : Tap this icon to set labels for the message to help organize your messages.
Unread : Tap this icon to return the message to an unread state.