If you insist on starting, start by considering it gambling and any money you put into it as gone. No matter what happens to that number, it's not real money if it isn't in your bank account, so don't get attached.

After you're in the right mindset, I use TD Ameritrade and found their videos pretty educational from the POV of an absolute beginner. Their app is pretty good too, though I honestly haven't shopped around (my mom set me up with an account with them when I was a teenager so I just kind of defaulted to using them).