How to specify a permission as an access argument?
This is based on Drupal 6 but I doubt it has changed.

access arguments returns true if the user has the permission specified in the array, however, it does not make sure to create that permission if it doesn't exist. If you want to use a module specific permission you need to define it using hook_permission (hook_perm for D6). If there already exists a permission that will suit you needs you can simply call that instead, though.