Alright. So for a bit of backstory I am 16 and until this point in my life I have been a rugby player in the UK, and honestly a very good one. I truly believe I had a shot at a professional career, and was lined up for some scholarships. However a recent seizure led to me being taken to a hospital where it was discovered I had a partially inoperable benign brain tumour. It is above the brain mass that controls movement on the left side of my body and as I am left handed they want to avoid surgery at all costs unless my seizures become more frequent, so basically it stays and I take pills forever. At my age even if I did get surgery (which they don't want) it would be a minimum of 2 years before I'd be allowed to play rugby again. That basically means I've missed my shot and I won't get another, pro rugby is done for me.
Now it took me some time but I've accepted it and moved past that fact, and I've decided I need to find a new team sport to play, as although I enjoy cycling it misses a certain thing that I love in competitive team sports (I'm not trying to go pro in a different sport, don't worry). As a result I've looked at joining a five aside football team, but I know very little about football. As in I probably have about 200 minutes combined time on a football pitch my whole life. Never played it with my family, got out of it at school, played rugby with all my friends, etc. So I am clueless. I've been googling the rules for the last 45 minutes.
I've tried to ask friends and PE teachers, but I am an anomaly in England, someone who managed to just never play football is very, very rare.
I know I've gone on but basically what would be the essential things to learn before even trying to join a five a side team if you were absolutely, completely new to the sport?