In Magento 2 you cannot perform the reindex from the admin panel. 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.
To reindex from Magento 2 admin panel:
1. Install Magefan CLI extension to see a new menu item "System > Command Line" to be added to the admin menu.
2. Enter your current admin user password (for security reason) On "Comand Line" page and enter the reindex command.
3. Press ENTER to start the reindexing after you have entered the "php bin/magento indexer:reindex" command.
With Magefan CLI module, you can run any other Magento 2 commands.