There isn't really that much to it
The 360 is considered a basic spin when skating street, and there isn't much to it!
Stand still on a flat surface. Now try to jump up in the air, and try to spin! Look over your shoulder to the side you're spinning, it makes your momentum cary you around to the side. When you can do this, and then landing facing the same way you did when you set off, you have done a 360.
Go to a gap, flyout, launchbox, or something you can set off from. Skate up to it with a moderate speed and spin around just like you did on flat ground. Don't pull your legs up to your body yet - just try to spin around with your legs straightened out.
When you can do a 360 over an obstacle with your legs straightened out, it's time to pull them up to your body. This might make you loose your balance, but just try a couple of times, and it should be there!
Now it's time to grab your skates too. Start with a mute air - that is a grab where your legs are kept together, and you reach with one arm and grap the opposite side's skate. Now you can do other grabs, such as stale japan, liukang, safetygrab, flying fish, etc.