You probalby installed odoo server using some cook-book... and obviously you lack linux skills..
Most likely this error is relate to file system permisiions, you are logged to your server using your user account, and you are trying to write to a location owned by openerp/ odoo system user... (something like /opt/openerp or /opt/odoo)

To find that out, from terminal type 

ls -la /opt/openerp/addons # or your full path to addons folder

see which user/group ownes that location... 
from this point on.. you need to find most apropriate way to put files there... using sudo, or correct user or something... 
this is only to point where to look for solution.. 

hope it helps

Thanks a lot Ludovic :) apparently it works !! 

Can you tell us more?

Maybe you try to copy your module in a restricted permission directory …

So, you have to have right permission to do it.

But' the good way for add custom modules is to them in an other folder and add the new path in your odoo configuration file: /etc/openerp/openerp-server.conf