You can find tutorials, generally they say something like pretend you're shooting video, shoot from the hip, or pretend you're taking a picture of something else. These all work, or you can just be as obvious as you want if that's what you're going for. In general, being obvious is perceived as less creepy if you're close.
Regardless of technique, think of what kind of imagine you want. I used to like having people stare into the camera so I'd raise my camera to my eye, maybe even ask for permission, now I'm shooting more from the hip and very close. Busy people won't notice anything around them, those that are alone are a lot more aware.
Experiment
Try to both have an image in mind, and to react spontaneously as you walk, see what style suits you better, and the same goes about subject matter. If Central Park doesn't inspire you, try something more crowded, indoors, windows, the subway, etc. Try walking fast, and walking slow, and standing still. If you have a DSLR try using your phone to begin with, or a smaller camera . Getting comfortable also means finding what works for you.
Be quick, that's very important to get the right moment, to some extent regardless of how you approach street photography, good moments are brief. To do so you may need to use zone focus, restrict to only one focal length you know well so you can previsualize the framing, and crop if that's what you need to do.