In Magento 2 you cannot perform the reindex from the back-office. To make a reindex you need use PuTTY or another terminal application to run the CLI commands, e.g. command for reindex:

php bin/magento indexer:reindex

With FREE Magento 2 Command Line (CLI) Extension by Magefan you can run CLI commands directly from Magento 2 admin panel.

Once you install Magefan CLI extension a new menu item "System > Command Line" will be added to the admin menu.

Magento 2 Command Line

On "Comand Line" page you need to enter your current admin user password (for security reason) and enter the command to start reindex.

Reindex Magento 2 From Backoffice

After you have entered a command "php bin/magento indexer:reindex" press ENTER to start the reindexing.

Result:

Reindex Magento 2 From Admin Panel

With Magefan CLI module, you can run any other Magento 2 commands.