The law of attraction is the idea that if you will something, it will happen. So, if I put enough positive energy into wanting a car, I'll get a car. But, it's not a direct thing, so I may get a non-working car if I don't ask for a working car. One of my friends tried it and got a working car with no floor, no tail lights and an oil leak, it was a $50 death trap, lol. But, he then sold it for parts and bought a better car with that money - so it did work in the end.
I'm sure you already knew how it works, but I'm explaining so you understand how to make a shrine. Your shrine will be a place to focus that positive energy on the object you desire.
To make a shrine, visualize what you want and put your energy into that dream. Then, if you like, make a collage featuring that thing. This would be your shrine. So, if you want a brand new car, make a collage of that car, pictures of it, notes on why you want it, plans to how you're going to get it, etc.
This is just one thing you could do, you could also take a single image of what you want, or a note detailing your dream (what you want) and tpe it up somewhere you will see it a lot. Burn incense or a candle near it to help you focus your energy towards it.
How you do it is really up to you. The whole point of a shrine is to make a place to build up your positive energy. If you are happy with what you made, it should work. Just don't expect what you want to fall out of the sky. If you feel a pull towards a path that will get you to your dream, follow it.
Hope that helps, good luck!