Never smoked before - super nervous

I have constant lower back pain that's better right now, but i normally take some pain meds before bed. got legal today in ca and ordered some pre-rolled god bud joints but i don't even know where to start. how much is enough? never smoked before in my whole life. i'm not a small dude.

nervous smoking by myself, don't know anyone in this city. one hit won't kill me will it?