filezilla.sourceforge.net
Once you've got an ftp program installed on your machine, set it up with your host's ftp details (hostname, username, password) then upload the module from your hardrive to the /modules/ directory in the root of your XOOPS installation on the web server. Once this is complete you should be able to see the new module listed at the bottom of the screen in Admin > Modules. Click on the install icon there and away you go.