`mount` - mount a filesystem, or list what is mounted

mount [-t TYPE] [DEVICE DIR]

Options you will use

--bind: Mount a directory (or file) at a second place too: mount --bind OLD NEW.
-a, --all: Mount everything in /etc/fstab that is not mounted yet. The way to test fstab without a reboot.
-o OPTIONS: Mount options: ro, rw, remount, noexec, nosuid...
-t TYPE: The file system type: ext4, xfs, nfs, tmpfs...

Try mount in a real terminal Free, in your browser - a real Ubuntu terminal to try it in, with missions that check your work.