The email link can be found on the left hand menu in the course.
To send an email make sure to first click on the email link in the course menu. Once you have clicked on the email link you should be taken to a page that looks like this.
From this screen you can click on inbox to see your messages or you can click on sent to see the messages you have sent to others.
To create an email simply click on the create message button. Which should lead you to the picture below.
On this screen you need to click the TO button, which should open up a box with all the students and teachers name. To select who you wish to send the message to just click on the person you wish to send to and then click on the right or left arrow in the purple box in the screen capture.
Now all thats left to do is to fill out the subject of the letter and to write the message that you need to send and then click on the submit button at the bottom.