How do I reindex catalogue on Magento 2? ‘reindex’ dropdown not available

New products are not appearing on the live page. I understand I have to reindex the catalogue and clear cache for them to appear.

Selecting: system > Index Management

When setting all to ‘update on save’ the boxes are red and do not have a current date/time.

When setting all to ‘update by schedule’ the boxes are green and do have today’s date/time but this does not make a difference to the live site – I’m not sure of the difference between these two options.