Unity is straightforward to install. You can download the executable here (for the OSX installer, click the link that says‘developing on Mac OSX?’). Let it download, run it, and follow the installer instructions. When the installation is fin- ished, a window entitled ‘activate your Unity license’ will appear. Check the box marked ‘activate a free 30-day trial of Unity Pro’ and click ‘OK.’
Congratulations! You know have a 30-day trial of Unity Pro. When the trial expires, if you don’t want to buy the pro ver- sion, you can switch to the free version and keep your existing content.