if you want to share a directory between guest and host OS, then you need to create a shared folder. adding virtual disks won't help you.
Thus create a shared folder to real time share data . how ever you need to have vmtool installed to do this successfully.
http://www.vmware.com/support/ws4/doc/running_sharefold_ws.html
http://www.howtogeek.com/howto/ubuntu/how-to-share-folders-with-your-ubuntu-virtual-machine-guest/

Read the following links on how to install vmtools

http://www.vmware.com/support/esx2/doc/esx2-rhel4-update.html
http://www.vmware.com/support/ws5/doc/ws_newguest_tools_linux.html
http://www.howtoforge.com/vmware_tools_on_linux