Your first trial of Illustrator or Photoshop can be got on the adobe.com site, here for Illustrator, or here for Photoshop. Just click the free trial button at the top of the page when you get there. It only lasts 7 days, but you can get a free trial of older versions that last a month.
Below are the links to the adobe site where you can get a free trial of the various versions of Photoshop and Illustrator.
You are allowed to have different versions installed on your computer at the one time, with the same adobe account.
All these links send you to the Adobe site and you will need to log in with your (free) Adobe log-in details. After you get on the adobe site, scroll down the page to select the program you want to download/trial.