You will want to find out where your module lives -> determine whether it lives in /sites/all/modules or in /sites/default/modules
Download a copy of the latest 7.x-5.x from our drupal.org project page: https://www.drupal.org/project/webform_civicrm
Unpack that tar.gz
Then replace what you have in /sites/all/webform_civicrm or /sites/default/modules/webform_civicrm with that new copy you just downloaded/unpacked using sftp or scp (depending on your access to your site)
Running database updates is a good idea - always do that after you update any module. You can do that by typing /update.php behind your base URL in the browser - or go to Reports -> Status Report and follow link (it should be reporting to you whether there are any pending database updates).