This is the MyCloud Mirror forum rather than the EX2 one, but the two devices are probably close enough that what works on one should work on the other (but I include the caveat as dashboard settings etc may be slightly different).
Firstly if you have uPNP enabled on your router, the simplest way to do the port forwarding is to use the port forwarding settings on the EX2 (under the settings>network menu on the dashboard - on the MCM it’s at the bottom of the list) where you can have it automatically tell your router to forward ports 8080 and 4443 to it (the two webdav ones, for http and https access).
The next question is what IP address are you trying to use for the external access. It won’t be your 192.168.0.8, as that’s the internal IP address of your EX2 on your local network. You need to use the external IP address of your router, which should then forward the requests on ports 8080 and/or 4443 to the EX2 via the forwarding rules you or it set up. You should be able to get that IP address from your router’s dashboard display.
But also note that unless you have a static IP address set up with your ISP, that external IP address may change over time. This is where dynamic DNS services like NoIP.com, dnsdynamic.org or duckdns.org (or many others, do a google search for many more) come into play, as they can give you a url (mysitename.noip.com or suchlike) which they then resolve to your external IP address. They have various apps that you install on your local network (or in many cases the router could support them directly) so they can track what your external IP address actually is to keep the association between the fixed url and the possibly varying IP address.