It sounds like you're looking for a way to play on your PC. While the game is not officially available as a "free full version," there are legitimate ways to get it or try it out.
If you're planning to install it on your PC, here is what you'll need according to the Steam listing: : Windows 10 SP2 or newer. arma-tactics-free-download-pc-game-full-version
: You can earn experience points to level up characters and unlock specialized weapons and equipment. It sounds like you're looking for a way to play on your PC
: You control a four-member Special Forces team through story-driven missions and generated objectives. : You can earn experience points to level
: There are no set "rails" or paths; you decide how to approach each mission using tactical thinking. PC System Requirements
: If you'd rather not install it or don't meet the system requirements, you can play Arma Tactics online through cloud services like MTS Fog Play .