Tap the internet browser icon.

Tap the address bar.

Key in mail.google.com and tap arrow right.

If it's the first time you use the application, you need to log on.

You can now use the application.
Gmail isn't part of the original application package and therefore only a general description is given here.
You have a number of options, such as:
Send emails
Retrieve and read emails
Reply to emails
View list of contacts
Create a new Gmail account

Tap the home icon to return to the home screen.