First, you need to be a good communicator, an example is; going up to someone FIRST, maybe a compliment would be okay, or even just a, "Hi", to start a conversation!
Next, make sure to come up to them just a bit calm, it's okay to be nervous- but just make to sure you can even say hi before going up to them. You could scare someone away if you go up to them being wild as ever.
Then, you could simply say, "How are you?", or anything, a question, you can even say, "Hello!", again, to end up starting a conversation with the person you're trying to communicate with- and perhaps they may be the type of person that likes talking and making friends.
Also, make sure to smile little bit, put some excitement into your voice, that'll make them want to hear you talk, they'll start to get a bit more excited with the way you guys are starting to get along and become friends. After, you get to know each other more, you can actually ask if you wanted to be friends.
Finally, you guys are friends! Depending on which type of person they are also depends on their answer. If they're an introvert, they'll most likely say no due to how much they enjoy alone time, if they're an extravert they'll 100% say yes, due to the fact that they like talking to anyone and like being around people!