Once downloaded, double click on the Final Cut Pro Trial .dmg file. After mounting the virtual disk image, double click on the Final Cut Pro Trial pkg. A dialogue box will open to walk you through the installation process. Make sure to agree to the license agreement, and then click install. You will be asked to enter your User Password. Type your password and click Install Software. When the installation has finished, close the window, and navigate to your Applications folder. Scroll down and double click on the Final Cut Pro Trial.app to launch it. A dialogue will inform you that you are starting your 30 day trial and give you the option to purchase the app. Click ok.
Next, Final Cut informs you of changes that have been made to the software in the latest version. Click continue.