How to transfer files between ghostbsd and usb stick？I have read some articles,but still don't know how to do.Any step by step instructions?

OK...
The MATE desktop allows you to open discs and folders with the Caja program. [Applications ? System Tools > Caja]
Then, graphically you drag and drop between folders and discs.
If you see an icon appear on the desktop called da0, this is the first usb device plugged in. the second is da1.

From a terminal [Applications ? System Tools > MATE Terminal] you can do the same once you know the cp command and pathnames.
By default, MATE places the first USB device at da0 in a folder called media. Thus the path is /media/da0.
Of course the USB device must be able to hold files... so it needs a file system (FAT32, NTFS...) - this is achieved by formatting the USB. The default format on a USB is often FAT32. This is best as it is more universal across OSs.
Formatting can be done on any pc.

When you put the usb device in the usb port MATE looks for the device, determines the file system type and mounts the device [da0] in the /media folder.

Hope this helps.
Let me know if you need help formatting devices....

Steve

I can not see my usb in Caja.
I see four folers under /media, ada0s1,ada1p2,da0s1,ugen0.3.My usb mount to which folder?
When I run mount in terminal,I get following results:

/dev/label/rootfs0 on / (ufs, local, noatime, journaled soft-updates)
devfs on /dev (devfs, local, multilabel)
tmpfs on /libexec/rc/init.d (tmpfs, local, noexec, nosuid)
procfs on /proc (procfs, local)
linprocfs on /compat/linux/proc (linprocfs, local)
tmpfs on /compat/linux/dev/shm (tmpfs, local)
procfs on /proc (procfs, local)
/dev/fuse on /var/run/user/1002/gvfs (fusefs)
/dev/fuse on /var/run/user/1002/gvfs (fusefs)

Which is my hard disk?

That's odd.
GhostBSD journaled file system is ZFS. Yours doesn't show this.

type
uname -a
in a terminal.
Doest it report:
13.0-STABLE FreeBSD 13.0-STABLE GENERIC amd64
?

I'm on 12.2,
12.2-STABLE FreeBSD 12.2-STABLE GENERIC amd64

You are out of date and to fix your automount issue do this.

I upgrade to freebsd13,follow the instructions on this site.I didn't delete cache file.
I downloaded all the files,but I don't know whether it finish the installtion.
When my laptop power on,I can only goes to freebsd terminal.
I get error message:error resolving pool 0.freebsd.pool.ntp.org:
Non-recoverable failer in name resolution.
How to go to mate desktop?Or how to fix my OS?thanx

Most likely if you have not removed this /boot/zfs/zpool.cache you will not be able to boot properly.

/boot/zfs/ directory is empty.
How to fix my os?

Oh, are you running on an Intel or AMD GPU?

If so, drm-fbsd13-kmod might be missing login in the shell and run the following command: On reboot, it should go to the GUI login screen.