You want a good VPN. Personally, I believe it's worth paying for things like this because the free ones are frequently a source of adware, spyware, viruses etc.
But anyway,. On the regular internet, you can go to any number of sites to buy bitcoin. I was having problems because the bank weren't fans of the way I was using my bitcoin (and I know others had the same issue), but I started buying at Kucoin upon a recommendation. They're Chinese, so they don't care (was what I was told and it seems to be working ok).
The first time you use it, they will ask for some photo ID like a driver's license or passport, but it's usually just the once.
On logging into the site, you will need to complete captchas and possibly use an authenticator app. I don't use Google authenticator because it had bad reviews about being glitchy. I use this one, which has always worked perfectly:
https://play.google.com/store/apps/details?id=me.jmh.authenticatorpro
Once you've brought the required amount of bitcoin and it is visible in your account (don't worry if it takes a few minutes), you will want to withdraw it.
For this you need the address that you intend to send it to, be it your own wallet or one that you use on a website. It will ask you to enter this. Then you choose the Network you want to use. Chances are it will be the first one that says BTC (bitcoin).
Next you need to enter the amount you want to send..you can choose to send all if you wish.
Then you click complete.
Again you will need to enter a withdrawal code that has been sent to your email account and use an authenticator, for your own safety.
And that's it!
you may have to wait about 30 minutes for it to clear the Blockchain, but that's your money turned into bitcoin and where you want it
Now, if you're spending it on the darknet, this is when you turn in your VPN. Just don't go on there without it being switched on. It's like that dream people get where they go out without their trousers on.