You'll have to setup port forwarding. This can be done by logging into your router.
If you don't have access to your router, you can try mStream's auto port forwarding feature. It will use uPNP to try to automatically configure port forwarding
Just throwing this in, as I thought it was pretty cool.. If you use google domains, you can update via dyndns request. I haven't tried it yet, but there doesn't seem to be a charge, and would probably be easy enough to setup a cron job.
If you don't have access to your router, you can try mStream's auto port forwarding feature. It will use uPNP to try to automatically configure port forwarding