Hello and welcome to the forums!
Unfortunately, the deal Ironhide Studios had with Armor games was only for a two game deal, Kingdom Rush, and Kingdom Rush Frontiers, and due to the deal ending, amongst other reasons, like not being created in a compatible format, Kingdom Rush Origins has not and will not be released onto Armor Games. Currently it is only a mobile release.
Ironhide (namely, the old community manager, The Tats) wrote this
Open Letter on the issue, their reasoning, and possible futures. Do bear in mind that this was written over 2 years ago, however.
(Full link if that doesn't work:
https://www.ironhidegames.com/News/Details/101 )
Fortunately, I do have good news for you - Both Kingdom Rush and Kingdom Rush Frontiers have been released on Steam, the release of Frontiers is the most recent Ironhide activity in fact, and because of the success and ease with which the ports to Steam took place, The Tats did mention plans to port Origins to Steam were in the works. (The Tats is no longer Community Manager here, however there isn't much reason to believe a Steam port for Origins isn't coming eventually, especially as the port is fronted by a separate, smaller studio, meaning the current plans Ironhide has don't have to take precedence over it)
Speaking of current plans, Ironhide has announced Iron Marines, a new and different venture set in space, (possibly with a cameo or two from Kingdom Rush - Edih Nori!), as well as a fourth Kingdom Rush game, also announcing their intention that both be available on both Steam, Android, and most other platforms.
I hope this can be some solace to you. If you don't have Steam then I am afraid Origins will not be available on PC (although I should point out the Kingdom Rush games on steam are pretty cheap during the steam sales, and come with all the Heroes, albeit unlocking stronger heroes as you progress throughout the game). Beta Testing opportunities are often offered to Forum members (we're waiting for the Iron Marines beta currently), so if you do have a way to play the newer games (Steam or any recent-ish model of an Apple/Android/Google Phone), you would probably have the opportunity to help in the creation of the games (and I believe get a mention in the credits).
I must also shamelessly plug the rest of the forums, we're a little barren at the moment due to the lack of recent content, however we do have an active Discord I could link you to if you so choose, although the forum would be the ideal place for discussion. For instance if you have your own ideas for heroes, towers, or even full levels for the games, the Fan Fiction subforum would make a great home for them, and I and others would be that happy to offer feedback and compliments. We also run semi-regular contests, and there are currently threads discussing Future Contest Ideas, Recreating and Balancing existing heroes, and Burning Skies, a hypothetical Mini-Campaign the forum is creating via a number of polls, headed by the excellent Big Bad Bug.
My apologies for how long this post is. I hope I have answered your query.