You have to add a cronjob that triggers the scheduler now and then. Otherwise just nothing will happen.
For example, after open your crontab for editing with crontab -e
add:
*/15 * * * * /usr/local/bin/php /home/bob/www/typo3/cli_dispatch.phpsh scheduler
Of course those paths needs to fit your php binary and your typo3 folder. With this cronjob your scheduler will be called every 15 minutes. Each time it will check if any scheduler tasks are late and if so, will start them.
You find the complete how-to here (from the official scheduler documentation).