From the Start screen, swipe left to display the apps list. Alternatively, tap All apps (located in the lower-right, may require scrolling).
Tap the email account (e.g., Google Mail, Yahoo,Hotmail, etc.).
Tap new (located at the bottom).
From the 'To' field, enter an email address or contact name. Alternatively, tap the Plus icon (located in the upper-right), tap a contact then select the email address (if applicable). Repeat this step as necessary to add additional recipients.
From the 'message' field, enter the message.
Add additional info as required (e.g., Subject, Cc/Bcc, attachments, etc.) then tap send (located at the bottom).