One can very quickly observe a child, what is the general nature of other kids. Age is not a barrier to understanding and observing so you will do just fine. See and understand what they may be interested in and think on lines similar to theirs. Try and understand their interests with the help of observation and prepare yourself to be more willing to adapt.
Talk to the other kids in an informal manner. There is no need of formal introduction as that works more for elders but not for kids. Once you get into a bit of chatter, you can discuss the things of your liking. Generally talking to other children about sports or video games or even television programmes can be a good way to start a conversation.
Be at Ease
There is no reason to be feeling stressed. You are not looking to pass a major exam but just looking to talk to another kid. They are most likely equally nervous as you are and it takes time to get used to meeting people that you do not know. Do not do any erratic movements as these will send a negative signal about you to the other kid.
Act Your Age
Everyone has their own way of doing things. Some kids act mature well ahead of their age and you can be one of them. Do keep in mind that everyone that you meet may not be like that. So you can bring out your childhood nature and have fun. Keep the serious stuff for adults or if you find someone similar to you.