Tuning my guitar

I am really a beginner. I am trying to set my notes, and I don't have a piano to hear, how can I tune my guitar

I would really recommend a tuner. But if you can't get access to one, and you have a good ear, you can use the tuner here on this site for example:

http://www.guitartricks.com/tuner/tunerpop.php

You will get all the reference notes there.

I use it myself every now and then.

That's only for full access members. Try this one:
http://www.online-guitar-tuner.net/standard-guitar-tuning.php

But buying a tuner is definitely the best recommendation to give to you. Go to your local guitar store and get one for around $30 that will be good enough to last you a long time as a beginner.