Long exposure light photo, Nikon d3200?

How can I take long exposure photos with this model?
Can you give me step-by-step tutorials, or good videos?

What no help from the Owners Manual?

Pages 55 and 57 covers on how to change the shutter speed
http://www.nikonusa.com/...200_EN.pdf

Three steps.

1.use a tripod

2.set your aperture on aperture priority to f/10

3.use your camera's 10 second timer to avoid blur from you pushing the shutter release.

That's it other than frame and focus.

There are many tutorials and videos about how to set your camera up for fireworks (setting focus to manual, focus point, etc) that you can google or find on YouTube.

Here is one of the better ones:

Just use one of those videos to setup your camera, except, then change your shutter speed until you get the desired exposure. It is somewhat trail and error.

How long is long? In manual mode you can set exposure up to 30 seconds. If you set the exposure to bulb, and you set the mode to work with the infrared remote, then the exposure will start with one button push of the remote, and end with another. If you never push the remote a second time the exposure will end in 30 minutes. Seting long exposure noise reduction can help decrease hot pixel noise, but even with that hot pixels will occur after a few minutes.
Getting the camera focused in very low light can be tricky.