You buy it from a store.
As for the whole mac vs pc thing, it depends on what you plan on doing. If you want to use solidworks or alias, get the pc. Macs do have virtual pc but it still isn’t fast enough to run a good cad package. I’m a professed mac nut, but I still see the need for a pc because I use solidworks most every day. If you’re just going to use photoshop, illustrator, maya. I’d get the mac. But if you want an actual CAD package, there really isn’t one for mac.
Also, your posts will seem a lot more credible if you use proper English, like using punctuation properly.