Your passport should be renewed about 7 months before the expiration date. As it is a simple renewal you will be able to renew by mail. Send in the renewal form, new passport photos, and your current passport. And of course, your $$!
Here is the information and form you need:
https://travel.state.gov/content/pas...rts/renew.html
My rule for my family is that your current passport is fine for traveling to Europe until 6 months before the expiration date.