You buy the growkit. You keep it in an empty compartment of the closet. You disinfect that compartment carefully. You only ever open the growkit wearing fresh gloves, having washed and disinfected hands and re desinfexted the area in which you open it.

Your main enemy is mould spores. They float in the air. Imagine you have a sterile lab like where they make co outer chips or sth

You follow the advice that comes with the growkit to the letter! Especially on the water you put in there and the soaking of the substrate!