Content Admin Search Tool Drupal 8
VBO doesn't search, it only gives you the interface to select items in the Views results and perform actions on them. 

To construct the search you want you can use ordinary Views with the Combine fields filter filter, here's one video tutorial: Search across Fields in Views using Combine Fields Filter in Drupal 8, or use Search API for something more advanced. 

Once you have the search working you can add the VBO field if you need to do some actions on the found items.