When the ground is warm. You need to mix amendments in your soil depending on where you live you might want to just replace the soil. Easiest, best mix where you can get all the ssupplies@ lowes/HD/walmart
Peat moss
Perlite
or instead of peatmoss and perlite, a base like pro-mix or black gold. Black gold will need some perlite.
Lime
Bone,blood meal if you'd like
Some shit. I use 3-4 week old chicken shit sittin in the sun. Basically any shit will do
Then I usually water with miracle gro or jacks classic during late veg and flowering, the cheap shit. Expensive shit isn't needed for weed. Its a weed.
You can also make some shit to water with I seen
Put some shit in a gallon container, put a little fishtank bubbler in there
let it bubble for 2 hours and thats some potent water
P.s. google is a growers good friend
hope this helped