I grew mushrooms about this time last year too. I remember covering the box with some old shadecloth, probably because the lid would have touched the soil if I had replaced it on the box. I think I used the shadecloth to maintain darkness and humidity. Mine grew in the shed, so garage might be most convenient for you. (Cupboard should be OK, but seems a little yucky, somehow.)

What I found hardest was keeping the moisture level correct--moist without being wet. I watered with a small beaker initially, then usually sprayed it with water every day thereafter, occasionally watering with a beaker when I was afraid the mix was growing to dry out.

You should have a lot of fun growing them.

Lid on!

For next time, if you want a kit with better instructions, go for Cali Grow Kits -- the manuals are super-clear and even illustrated.

Good luck!

I tried a kit from Garden Express last autum - they never grew at all - even after following all instructions. But I have since been informed that they only grow in spring and summer, so you never know - they might start growing soon.