I'm gonna type this from memory.
So you need spores, and you need a grain.
Buy a dozen ball mason jars with lids and rings.
You only need six. Trust me, it will grow plenty of shrooms.
Buy 2 lbs of popcorn. Simmer it in water for an hour. Don't boil, but just bring right to below a boil and simmer it. It will absorb the water.
Drain the popcorn in a colander, and let it air dry for about an hour. Stir it several times to all the water evaporates.
Put the corn in the jars. edit - leave about 2" at the top of the jar, you will need it later to shake them.
In the lids of the jars you need to make two holes. 3/8 inch. One gets a silicone injection port. You can order 100 for like $5 on amazon. The other will get covered with 2 layers of 3M Micropore tape.
Put the modified lids on the jars and tighten down the rings.
Cover the lids with foil, to keep the tape from getting directly wet.
In a large pot, put a few inches of water, some extra jar rings in the bottom to act as spaces, and then steam your jars of corn for 2 hours. You will need to add water every so often.
Then, let them cool over night.
Now, inject 1ml of spores. Shake your spore syringe well beforehand to break up any clumps. You only need 1ml per jar.
Put the jars somewhere dark. Back of a cabinet. After a month, check them. If the grain is not totally covered in white fuzz, bang the jar against the counter and break the grain up and shake it. Then put it back. Let them sit another few weeks until they are entirely covered in white fuzz. Thats the mycelium.
Now you need to make some CVG. Its coco, vermiculite and gypsom. Watch the boomer shroomer video on it, she shows you how to make it.
Mix 1/3rd innoculated grain from your jars with 2/3 CVG, then apply a thin 1/4" layer of CVG over that, in a plastic shoe box. You want this to be maybe 1" thick in total.
Put the lid on the shoe box, and put it somewhere cool (68-72*), with light during the day. I used my bathroom with a LED light on a 12 hour timer. They will do fine without the light, but they will grow towards light, and without you get weird shaped mushrooms. I just aimed the light into the cabinet they were in, but didn't like try to create a point source.
In a few weeks looks in your boxes (I hope you bought clear ones) and it should look like the entire thing is covered in freshly fallen snow. If you see any green, do not open it, throw it away without opening. Thats mold and will spread like crazy. From here on, you need to introduce oxygen several times a day by removing the lid and fanning the surface with the lid. Like 3x a day is fine.
You should see mushrooms start growing within a few days, and in a week to week and a half have a harvest.
Harvest, rehydrate your block of mycelium, put the lid back on, and go for another flush. You can get 4-5 flushes, and each one get 50-100 grams wet mushrooms per shoebox.