You can access the web admin from anywhere, I set the options so I can access it outside through port 9000 using a dedicated port or otherwise the default is port 80 so it will depend on your setup as to which one you use. I use port 9000 as I already have a dedicated web server on port 80 for our home page.
or if you are using another port rather than port 80 then you would need to change it to the following example http://your_ip_address:9000/lmce-admin
where 9000 is the port you have specified in the outside access page of web-admin, this would then have to be port forwarded in your adsl modem router as well. For internal on any pc just use http://192.168.80.1/lmce-admin
with your login details as per Kezza's post.
Hope this helps