How can I view my computer on my TV ?

[Cage]

OK, I got the NBN, 100Mb/sec down and 40Mb/sec up. Bloody ripper, and not before time , but that's another story.

My router streams directly to my 'Smart TV' (is that an oxymoron ?) and I can watch Catch-up-TV and all that sort of stuff which is great with 100GB of download as I don't even need to use my HTPC, an acronym I use to refer to my old computer, which I set-up as a recording device.

I now have an idle TP-Link TL-MR3420 router which I used to download mobile phone updates via the internet and I think, and I'm probably wrong, if I had another RJ-45 Port I could use it to stream my 'puter to my TV.

Is my RJ-45 Port piggy-backable (is that a word ?) or would that confuse the crap out of my computer?

My question is how can I view my computer screen on my TV ? My computer only has one RJ-45 LAN Port which, obviously, my NBN router is plugged into.