Find some quick tips about how to tune your guitar here!
In this video I'll show you how to tune up using the free app "Guitar Tuna" which you can get for most devices.
This link will take you to their website if you want to find out more:
Here's a couple of things I don't mention in the video that you might find helpful.
1. Hit the letter name next to each tuning peg to hear how the string is supposed to sound. This is really helpful if your guitar is way out of tune.
2. Don't over tighten strings, they can snap.
3. The free version gives you access to 'standard tuning'. If you want to try other tunings you'll either need to purchase them in this app, or perhaps find your self a good chromatic tuner app, which will let you tune your notes to any pitch you like.