Add, mount, move shared folder from win10 host ubuntu 17.04 guest in VirtualBox

I am a retro - newbie (last used Linux back in 2004 - Mandriva), but I am confused / baffled.

I want to add shared folders from Win10 to Ubuntu 17.04.
So far, I've successfully installed GUEST ADDITIONS. (Which was a hassle in Kubuntu).
I've located the shared folder sf_name in root/media/username.
I added my username to the vboxsf group.
I can open it as "root." But I cannot access it from my username account so other software can easily see it.
I want to move the folder to home/username/Shared.
And in the future, mount the shared folder to that folder.

I cannot decipher the VB manual, and the various videos have contradictory instructions or they don't work on my system.

From the VB manual - - -
To change the mount directory to something other than /media, you can set the guest property :
/VirtualBox/GuestAdd/SharedFolders/MountDir.
I assumed that SharedFolders = sf_name; MountDir = /home/username/Shared (target)
So I entered /VirtualBox/GuestAdd/sf_SharedFoldername/home/username/Shared in the terminal.
“No such file or directory”

Was there something I missed in that simple sentence?
Was that a command to be entered into VB?

Or other variations:
"Protocol error" "Can't find folder" "You are a newbie - go away!"

Can someone please spell out the EXACT procedure to :

• MOVE a mounted shared folder

-and -
Set future reboots to

• MOUNT the shared folder to home/username/sharedfolder ?

Thank you.

UPDATE:
After rebooting, now I can "see" the shared drive in FILES and access them from other applications.
SIGH
. . .
I guess it is moot with respect to mounting to a different location.