http://gpp6nwvsps43b3mfacsh433uroo6uyjvvpr6tgj4jh4n5ngxt7rqbvid.onion/posts/storing-a-sensitive-document.html
Setting up and using a Tor hidden service needs additional expertise. Version 3 onion addresses are 56 hexadecimal characters long, which is far too long to remember and would itself need to be securely stored somewhere.