It's hard at first and then you learn to do it and get good at it. I still hate finding a new doctor, but that's because it's a tedious process full of disappointment when what you need is something most doctors don't do or advertise whether or not they do it (adhd meds mostly).
My mom died when I was around your age (early 20s). It was really hard not to have her there to help me learn to do such things, but I had to do it, and so I did it. I wish she'd taught me when I was a teenager, but oh well. Around that time I had to teach a friend how to do such things too and she found it absolutely liberating once she got the hang of it.
I'm in my 30s now, and my wife and I both have tasks we pass off to the other, often because of mental barriers or just struggling to start. But when push comes to shove we both are entirely capable of such things, we just have someone we can lean on and swap tasks with.
It's ok to be scared, but do it scared. It's ok to do it late, but do it anyways. You are capable of all this, and you'll be much happier once you build these skills and independence. The only way out is through and it won't be comfortable, but it will be worth it.
Oh and for the practical of how: look it up. The state department website says how to get a passport. Oh and if you have to interact with the government but are unsure of what to do, ask a local librarian. Not kidding, they typically even have common forms already printed out or they can help you find the information. They're good at finding information.