How to start mining bitcoin?

well to start mining all you need to do is download a mining client and join a network (i'd recommend ethereum).
but mining with a normal desktop computer wont make any big bucks anymore. its way too late. you kinda need a mining system which costs way too much to make profit out of it.

if you want to invest you could buy bitcoin and hope that you can sell them for more. but overall i wouldn't recommend mining for profits.