Don't freak out! It's easier than you think.
I know what you're thinking. It's really scary at first! Your violin is a brand new baby and you're super gentle with it. Maybe you've even imagined yourself breaking the strings when you move those pegs. Hey, it's possible! Strings can break, so make sure to replace yours if they are more than a year old. If your strings are new(ish) and you follow these steps, it's unlikely. And it's all part of the learning process.
In order to follow this guide you'll need a tuner. This can come in the form of an app, or an electronic tuner. Either will work just fine.
So let's walk through the process, shall we?
For your first few times tuning up, you might need to repeat step 2 and 3 several times. Don't fret! Trust your instincts and your ear.
If you find yourself lost in judging the pitch of a string, try humming the note that you're looking for–the tuner will play it aloud with the "speaker" button. If you vocalize the note you are aiming for, it will make it easier to judge the sound of your string against the true pitch.
Remember this is one of the most important parts of your set-up. If your instrument isn't tune, you can't play in tune! Learn this step and you'll be well on your way to playing with great intonation.
Good luck and happy tuning,