If you’re upgrading manually, you only use your FTP client to transfer the files from your desktop computer to your hosting server, nothing more.
If you prefer to work directly from the shell, simply use something like curl or wget to grab the WordPress tarball, unpack it, and move the files and folders to the appropriate location.
You want to take care to get the old WordPress files out of the way and not delete your existing wp-content folder which contains your active theme, plugins, and uploads. Also, if you’re working with the root account, confirm to be sure the new WordPress files and folders have the appropriate ownership and permission.
Alternatively, you could simply upgrade automatically from the WordPress dashboard. If you’re trying to update from the dashboard and getting a prompt to enter FTP credentials, then kindly see this: Enabling SSH Upgrade Access
Good luck!
