Slow down and start at the beginning... Virtualbox manager cannot find your usb devices? Is this correct? And who is "they"?
The usual procedure seems to be as follows:
1. Create a group usbusers and put yourself in it. (System>Administration>Users & Groups>Manage Groups>Add Groups)
2. In a terminal, type in lsusb and note down the vendor and product ids for the devices that you want to enable. i.e. That "Hewlett-Packard " entry (a printer or scanner?) has vid
id - 03f0:7804
3. In VirtuaBox's USB section add these devices, making sure you have the vendor and id numbers correct.
4. As a super user, edit the properties of the file /etc/udev, so that you can read and write to the file.
5. Reboot (JIC).