Photoshop is not free. If you want it, you can try the 30-day trial for free and decide if you want to pay for it. You have a choice of outright buying it for $699 (Standard), $999 (Extended), or you can pay a monthly/yearly subscription service to use it for as long as you pay.
If it's too much for you, then check out PS Elements. It's a hobby version meant for amateur enthusiasts, which is much cheaper. Otherwise, GIMP is a free Opensource alternative to Photoshop that's similar.