Tap the Home Button 
> Apps 
> Gmail 
.
The current Google Account is displayed in the header at the top
of the Inbox. If you have more than one account, you can switch accounts
to view the messages in each Inbox.
Conversations with new messages are displayed with bold subject
lines. To read a message in a conversation, tap its subject line text.
The letter icon (or contact photo) next to a Gmail message allows
you to select it and choose an action from the icons at the top of
the screen.
The Favorite icon 
next
to a Gmail message allows you to designate it as a favorite message.