As Photoshop is a copyrighted product of Adobe Systems Incorporated, it is not possible to access the application for free. Adobe offers a free trial of Photoshop that lasts for a month.
Download a free trial of Photoshop by clicking Photoshop CC on the free trial page. Answer the three questions Adobe asks to determine your experience level, and sign it with your Adobe ID. The download starts automatically after the survey. Once you install the application, click the Start Trial button to activate your 30-day free trial.
You can get an Adobe ID for free. Click Sign Up for an Adobe ID on the survey page to register.