I don't know how to set this up, but I saw on your other thread that you haven't learned some basics with the multiplayer plugin, like how to retrieve a game list and load it into a list - are you sure it's a good idea to jump to the expert level and setup a signalling server?
I believe it requires you to be confident with intermediate/advanced networking - you need to essentially setup a server, along with configuring a few things to make sure the signalling server works perfectly for any type of peer that connects.
Do you pay for dedicated hosting, or were you planning to try and do this on your home computer?
How much experience do you have with computer networking? You say you have a server, so I'm guessing you have some knowledge?
I replied in the other topic about this and I suggested using the official Scirra signalling server. I've been using construct around 10 years, and I often enjoy working on multiplayer stuff, and with all of that, I would still not buy a signalling server - I don't quite have a reason where I would buy it, even if my game had 1000 daily players connecting online, the free signalling server that Scirra provide would handle that easily.
Buying the signalling server only has downsides in my mind - like it costs money to buy it, costs money to host it reliably, costs you time as you have to maintain it or troubleshoot your server if issues arise, costs you time learning about all of this when it's not essential to learn for game dev (although it's always good to learn new things, but there's SO MUCH to learn, are you sure you wanna learn about RADIUS and STUN and stuff? If so, good for you, knowledge is power!). All this stuff that costs money and time, is available for free from Scirra - if the Scirra signalling server goes down, sure you may feel panicked, but at least you have a knowledgeable team that are hosting the server and will fix it themselves, all for free.