To allow remote connections on the Draytek 2862ac you will need to access the router interface through a web browser. To do this make sure you're on a device that is connected to the router, open a web browser, and then type the IP address of the router (192.168.1.1 by default) into the address bar then press enter. You will then be asked to log into the router.
Once logged in navigate to System Maintenance > Management. On the Management page you will need to tick "Allow management from the internet" and make sure HTTPS Server is ticked.
Once you have made the changes click OK at the bottom to apply them.