Ot the thousands of available contributed modules, there are a few every site should have. One of these is "pathauto" which depends on "token"and "cleanurls".

As the user which owns the site:

drush dl token
drush enable token
drush dl pathauto
drush enable pathauto

The defaults are fine except "admin/build/path/pathauto". In the section URL aliases, check the box "Bulk Generate".

Of course, you need "drush" but that is another story.