Correct...
The host OS is the operating system used to run Virtualbox.
The guest OS is the operating system being run by Virtualbox.
If you select the guest OS in VB,
click Settings, select Shared Folders from the lefthand menu,
then click the blue/green folder (+) icon at the top left of the window.
Select the Memory stick and click OK, and name the folder if you wish to change the name.
The drive will then mount ready for you to use just as you would in your host OS.