When you first set up your iPhone you should have set up your email account(s).
If you did not, this explains how to add one.
http://support.apple.com/en-us/HT201320
Then. Click the app with an envelope on it and click the square and pen symbol to write your message. When you have done that, press send.
To add the picture,
hold your finger on the message area.
A pop up will say select Select all Paste and then an arrow.
Click on the arrow and the pop up will change to insert photo.
This will take you to your camera roll to select the pic.