Very difficult unless you have a clean room. Growing mushrooms is really hard because of the cleanliness required. You'll need to make a spore print, then transfer spores to agar and wait for them to grow, then isolate the mycelium before transferring to a medium like grain to grow. Spore prints are dirty and if you just try to use one and put it in grain, you'll just get a bacterial or fungal outbreak.
I have only had luck with using a growth medium, like 8oz distilled water with 1 tablespoon of maple syrup, and pressure cooking that. Then, using a fresh syringe and in an extremely clean area, split a fresh mushroom in half, and take a sample of it with the syringe and then inject it into the nutrient liquid. About 50/50 you'll get a clean sample and in a few weeks have clean looking mycelium floating in the liquid. You can then use that nutrient culture to inject on grain to grow.
Weed is SO much easier to grow.