How do I buy 1st share?

Excuse me, I'm quite interested in investing but I'm still a bit new to this. Could you possibly explain to me how I can go about purchasing my very first share? I've heard it's a good way to diversify my portfolio, but I'm not quite sure where to start. Would I need to open an account with a brokerage firm? And how do I determine which share is a good investment? I'm also wondering about the costs involved - are there any fees or commissions I should be aware of? I'd appreciate any guidance you can provide on this matter. Thank you in advance for your help!