If you're new to Drupal, you might want to let Drupal handle not just the CRUD, but the actual database layout as well.
Go to structure->content types, create a new content type and go to 'manage field'. This is where you create the schematics of your information. Once you've populated this content type with fields a default drupal install will let you easily create, read, update, and delete the content you create using it.
If you are working in a premade non drupal database you'll either need to convert the data to drupal's tables, or you'll need to write a custom module and make all of the CRUD scaffolding yourself (effectively bypassing anything useful about Drupal)
Hope it helps,
Patrick