Glad they let you out of the hospital so quickly (relatively). I know of folks who had to spend literally MONTHS on a ventilator.
You got it several days before you started showing any symptoms. If you'd been careful with mask wearing and crowd exposures, then you most likely picked it up via "hand contamination", touching someone or something that was contaminated and touched your mouth or nose or even your eyes with the contaminated hand/finger.
I decon my hands (and any surfaces I touch getting in the vehicle - door pull, steering wheel, gear shift, my keys) using chlorox wipes on re-entering my vehicle, decon my credit/debit cards after handing them to a drive thru cashier, wipe down all groceries with 10-1 water/bleach ratio solution after I bring them home from curbside pick-ups at Wally World or HEB (Texas chain), etc. I put the mail in a box in the garage for 48 hours before opening it and decon my hands after handling the mail and the mailbox.
Since my 84 y.o. mother lives with me and is a double high-risk category, I've been super-AR about deconning everything and going only where is necessary.