If you own a license, you already have access. If you do not, purchase FL Studio Producer Edition (which grants access to all legacy versions) from Image-Line. This grants you the ability to legally run FL Studio 12 on your older Mac while also owning the modern version for future computers.
Released in 2015, FL Studio 12 brought massive workflow improvements that still define the DAW today: download fl studio 12 mac os x top
If you specifically need version 12 (for example, to match an old project or a specific OS), you can find it through official channels: If you own a license, you already have access
FL Studio 12 does not support Apple Silicon (M1/M2/M3) natively. It will run under Rosetta 2 on newer Macs, but expect potential latency issues. If you own a license