If you have these mushrooms around you, the spores are probably in the air and the soil. And you don't really need to inoculate anything.
But if you want to culture this, or some other type of mushroom, then you grow them in a liquid culture. This mushroom seems to be very poisonous, so people don't grow it. But your best bet is to get a sterile petri dish with mushroom growth medium, and shake the spores on that plate. Then after 1 to 4 weeks, when you see colonies growing, prepare like a liter bottle of liquid mushroom culture. Like a potato starch or yeast extract. Cover the top of the bottle with tin foil. Then put it in the microwave until it slowly boils, not blowing off the top. Until it is completely sterile. Then take a toothpick, burn it in the flame of the stove, then dip it in ethanol to cool it. Then touch the fungal colony on the petri dish, quickly open the tin foil cap of the bottle, and throw the tooth pick in, and cover the bottle permanently. Now, the liquid culture may require some agitation to aerate the liquid. But this may allow the flash to completely fill with this Amanita muscaria fungus. And then you can do with it whatever you'd like.
Assuming this fungus is easy to culture.
As for plant benefits, I doubt it matters.