1. Connect to your server using command line SSH connection. SSH credentials can be provided by your hosting partner. If you experience connection problems, make sure your IP is whitelisted.
2. Go to the root location of your Magento 2 installation on your server.
3. Set Magento 2 Production Mode / Developer Mode
php bin/magento deploy:mode:set production
php bin/magento deploy:mode:set developer
Note: Depending on your hosting provider, for some servers command 'php bin/magento' does not work, you may want to replace it with '/usr/local/php56/bin/php-cli bin/magento' or '/usr/local/php70/bin/php-cli bin/magento' .
Example: '/usr/local/php70/bin/php-cli bin/magento deploy:mode:set developer'