I want to install One UI 6.1/6.0 on my Galaxy Note 20 Ultra 5G With my PC but I cant really understand the tutorials, if someone can tell me understandable instructions what to do, it would be really appreciated, thanks.
You can't, unless you choose to gain Root on the phone, and in doing so, you can say goodbye to Knox, and any security features that require it, such as Samsung Wallet.
If you insist on walking this path, I would recommend joining XDA, find the Note20 Ultra forum, and do lots of reading before you do anything else.
