Can't find migrate setting in configuration
Using the Migrate Upgrade UI (easier)
  
  
  Migrate Upgrade is a UI for core upgrades from Drupal 6 and Drupal 7
  to Drupal 8. It's still under heavy development, so things may break.
  If something fails for you, check the issue queue first! There may be
  a patch. If not, check with the developers in #drupal-migrate on IRC.
  
  After installing Migrate Upgrade, visit your Drupal 8 site's /upgrade page. When you do you will see this helpful Home screen.
  
  


Source: Executing a Drupal 6/7 to Drupal 8 upgrade

Step 1) Install Upgrade Migrate module

Step 2) Go to yourwebsite.com/upgrade

Worth Noting


  If you have a Drupal 6 or 7 site you want to upgrade, install or update the Upgrade Status module to get a customized, up-to-date report on the status of your modules and themes in Drupal 8. Once you are ready, Drupal 8 core also includes the Migrate module to update existing Drupal 7 and 6 sites to Drupal 8 directly. Migrate is marked "experimental" in Drupal 8.0.0, but will be fully supported in an upcoming release


Source: Drupal 8.0.0 released